Medical Encyclopedia A: Medical Terms Explained

A-positioning (thoracic positioning)

Positioning with pillows placed under the back in an A shape, with the tip under the shoulder blades. It stretches the upper parts of the lungs and supports breathing.

Aarskog syndrome

A rare, usually X-linked developmental disorder mainly affecting boys. Typical features are short stature, a broad face with widely spaced eyes, short fingers and genital anomalies.

Aase syndrome

A very rare congenital disease with anaemia due to reduced red blood cell production and three-jointed thumbs. It is now usually classified as a variant of Diamond-Blackfan anaemia.

AAV vector

A harmless adeno-associated virus used as a “gene shuttle” to deliver therapeutic genes into cells.

Abacavir

An antiretroviral nucleoside analogue for HIV treatment in combination therapy. Before starting, patients are tested for HLA-B*57:01, because carriers have a high risk of a dangerous hypersensitivity reaction.

Abaloparatide

A bone-building drug similar to parathyroid hormone-related peptide, injected under the skin daily. It is used for a limited period in osteoporosis with a high fracture risk.

Abatacept

A biologic that dampens T-cell activation by blocking a required co-stimulatory signal. It is used in rheumatoid arthritis when other disease-modifying treatments are insufficient.

ABCD2 score

A score estimating the short-term stroke risk after a transient ischaemic attack based on age, blood pressure, clinical features, duration of symptoms and diabetes. It does not replace rapid assessment in a stroke unit.

ABCDE approach

A structured sequence for assessing and initially treating critically ill patients: Airway, Breathing, Circulation, Disability and Exposure. Life-threatening problems are treated immediately before moving to the next step.

ABCDE rule

Checklist for assessing moles: Asymmetry, Border, Colour, Diameter over 5 mm and Evolution (change).

Abciximab

An antibody fragment against the platelet glycoprotein IIb/IIIa receptor, formerly used in cardiac catheter procedures. It is no longer marketed in many countries.

Abdomen

Medical term for the belly and the abdominal cavity between the diaphragm and the pelvis. An “acute abdomen” means sudden, severe abdominal pain that needs urgent medical assessment.

Abdominal angina

Abdominal pain about 15 to 30 minutes after eating caused by narrowed intestinal arteries. Affected people often eat less for fear of pain and lose weight; the narrowings can be treated by catheter or surgery.

Abdominal aorta

The section of the main artery below the diaphragm down to its division into the iliac arteries at the level of the fourth lumbar vertebra. The intestinal, renal and gonadal arteries arise from it.

Abdominal aortic aneurysm

An abnormal bulge in the main artery in the abdomen that often goes unnoticed for a long time. Above a certain size there is a risk of life-threatening rupture; ultrasound screening is offered to men aged 65 and over in several countries.

Abdominal guarding

Reflex tensing of the abdominal muscles when the belly is touched. It indicates irritation of the peritoneum, for example from a perforated appendix, and is part of the acute abdomen.

Abdominal hair loss (liver sign)

Loss of abdominal hair in men that can occur as a skin sign of liver cirrhosis. It is caused by impaired breakdown of oestrogens in the damaged liver.

Abdominal pain

A common symptom with causes ranging from wind to appendicitis. Sudden, severe pain with a rigid abdomen must be assessed immediately.

Abdominal skin reflex

A superficial reflex in which quickly stroking the skin of the abdomen causes the abdominal muscles to tense, pulling the navel towards the stimulated side. Its absence can indicate damage to the pyramidal tract.

Abdominoperineal resection

Removal of the rectum and anal sphincter for a very low rectal cancer, requiring a permanent colostomy. It is chosen only when the sphincter cannot be preserved.

Abdominoplasty

Tummy tuck: surgical removal of excess skin and fatty tissue from the abdomen, often after major weight loss or pregnancy.

In depth: Tummy Tuck →

Abducens nerve palsy

Paralysis of the sixth cranial nerve, so the affected eye can no longer move outwards and looking sideways causes double vision. Causes include circulatory problems, raised intracranial pressure or inflammation.

Abelacimab

An antibody against clotting factor XI, injected monthly, that showed fewer bleeds than conventional anticoagulants in studies. It is in late-stage clinical testing.

Abemaciclib

A CDK4/6 inhibitor for hormone-receptor-positive breast cancer, also used after surgery when the risk of relapse is high. Diarrhoea is a typical side effect.

Aberrometry

Measurement of the eye’s optical aberrations beyond simple short- and long-sightedness, such as coma or spherical aberration. It is used before refractive procedures.

Abetalipoproteinaemia

A rare inherited metabolic disease in which the body cannot form lipoproteins containing apolipoprotein B. Fats and fat-soluble vitamins are barely absorbed, leading to fatty stools, failure to thrive and nerve and retinal damage.

Abfraction

A wedge-shaped loss of hard tooth tissue at the neck of the tooth, attributed partly to bending forces during chewing and grinding. Incorrect brushing and acids often contribute.

Abiraterone

An inhibitor of the enzyme CYP17 that suppresses androgen production, including in the adrenal glands and tumour tissue. It is given with prednisone or prednisolone for advanced prostate cancer.

Abrocitinib

An oral JAK1 inhibitor for moderate to severe atopic eczema. As with other JAK inhibitors, risks of infections, thrombosis and cardiovascular events must be considered.

Abscess

An encapsulated collection of pus in a cavity formed by inflammation, usually caused by bacteria. Typical signs are swelling, redness, warmth and throbbing pain; larger abscesses are usually opened surgically.

Abscopal effect

A rare phenomenon in which, after a tumour is irradiated, non-irradiated metastases also shrink, presumably through activation of the immune system. Combinations with immunotherapy are being researched.

Absence seizure

A brief epileptic lapse of consciousness lasting a few seconds, mainly in children.

ABSI score

A score for estimating prognosis in burns based on sex, age, inhalation injury, presence of full-thickness burns and the percentage of body surface burned.

Absolute risk reduction

The difference in event risk between control and treatment groups in percentage points. It shows the real benefit more clearly than relative risk reduction and is the basis of the NNT.

Abstinence

Complete avoidance of an addictive substance such as alcohol or drugs. In dependence, lasting abstinence is often considered the safest treatment goal.

Abulia

Pathological lack of will and decisiveness in which affected people hardly act or speak spontaneously. It occurs in frontal lobe damage, schizophrenia or severe depression.

Abutment (dental implant)

The connecting part between a dental implant and the crown or bridge, which passes through the gum into the mouth.

Acalabrutinib

A targeted Bruton tyrosine kinase (BTK) inhibitor for chronic lymphocytic leukaemia and mantle cell lymphoma. Typical side effects are headache, diarrhoea and an increased bleeding risk.

Acalculia

Acquired loss of the ability to calculate after brain damage, often in the parietal lobe. It is part of Gerstmann syndrome and distinct from congenital dyscalculia.

Acamprosate

A drug used to prevent relapse after alcohol withdrawal, intended to reduce craving. It is used as part of a comprehensive treatment plan with psychosocial support.

Acanthamoeba keratitis

A rare, severe corneal infection caused by amoebae from water, almost always in contact lens wearers. It causes severe pain and requires long treatment.

Acanthocytes

Red blood cells with irregular, thorn-like projections, for example in severe liver disease or rare inherited disorders. In urine, similarly deformed cells indicate bleeding from the glomeruli.

Acanthosis

Thickening of the prickle cell layer of the epidermis, visible under the microscope. It is found, for example, in psoriasis, eczema or acanthosis nigricans.

Acanthosis nigricans

Velvety, thickened, darkened skin in the armpits, neck or groin. It is usually a sign of insulin resistance and obesity, very rarely of cancer.

Acarbose

An antidiabetic drug that inhibits small-intestine enzymes that split complex sugars, so glucose enters the blood more slowly. Common side effects are bloating and diarrhoea.

Acceptance and commitment therapy

A behavioural therapy approach that helps people accept distressing thoughts and feelings rather than fighting them, and align their actions with personal values. Mindfulness exercises are a central component.

Accessory muscles of respiration

Muscles of the neck, chest and shoulder girdle that are recruited in addition to the diaphragm during breathlessness. Their visible use, for example with propped-up arms, is a warning sign of severe respiratory strain.

Accommodation (eye)

The eye’s ability to focus between near and far vision by changing the shape of the lens. It declines with age, leading to presbyopia.

Accommodative spasm

Cramping of the ciliary muscle with the eye stuck in near focus, so distant objects look blurred. Causes include overexertion, stress or medicines.

ACE inhibitor

Blood-pressure-lowering drugs (e.g. ramipril) that block the formation of the vasoconstricting hormone angiotensin II. They are used for hypertension, heart failure and kidney protection; a dry, tickly cough is a typical side effect.

Aceclofenac

A non-steroidal anti-inflammatory drug (NSAID) chemically related to diclofenac. It relieves pain and inflammation, for example in osteoarthritis or rheumatoid arthritis, with the typical NSAID risks for the stomach, kidneys and cardiovascular system.

Acemetacin

An anti-inflammatory painkiller of the NSAID group that is converted to indometacin in the body and used for rheumatic diseases and gout attacks. Like other NSAIDs, it can strain the stomach, kidneys and circulation.

Acenocoumarol

A vitamin K antagonist anticoagulant with a shorter half-life than phenprocoumon. It is used in several European countries and requires regular INR checks.

Aceruloplasminaemia

A rare inherited disease with absent ceruloplasmin, causing iron to accumulate in the brain, retina and pancreas. Diabetes, retinal degeneration and neurological disorders in adulthood are typical.

Acetabular fracture

A fracture of the hip socket, usually from high-energy trauma in younger people or a fall in older people. Treatment depends on the fracture pattern and joint step-off and is often surgical.

Acetabulum

The socket of the hip joint, formed by the ilium, ischium and pubis and edged by a cartilaginous labrum. A socket that is too shallow is the hallmark of hip dysplasia.

Acetazolamide

A carbonic anhydrase inhibitor that reduces aqueous humour production in the eye and bicarbonate in the kidney. It is used in acute glaucoma, altitude sickness and certain forms of raised intracranial pressure.

Acetylator status

The inherited speed at which the liver acetylates drugs such as isoniazid via the enzyme NAT2. Slow acetylators have higher levels and a greater risk of side effects.

Acetylcholine

A messenger substance that transmits signals from nerve to muscle and is involved in memory processes.

Acetylcholine receptor antibodies

Autoantibodies against acetylcholine receptors at the neuromuscular junction, found in most people with generalised myasthenia gravis. They are detected less often in purely ocular myasthenia.

Acetylcholinesterase inhibitors

A group of drugs that slow the breakdown of the messenger acetylcholine in the brain, including donepezil, galantamine and rivastigmine. They are used in mild to moderate Alzheimer’s dementia to stabilise memory and daily function for a time.

Acetylcysteine

A mucolytic intended to thin sticky bronchial mucus; its benefit in ordinary coughs is limited. In high doses it is the antidote to paracetamol poisoning.

Acetylsalicylic acid (aspirin)

Active substance against pain, fever and inflammation. At low doses it inhibits platelets and is used in vascular disease to help prevent heart attack and stroke.

Achalasia

A rare disorder in which the lower oesophageal sphincter fails to open, so food stays in the oesophagus.

Achilles tendinopathy

Pain in the region of the Achilles tendon, usually from overuse in running. Eccentric exercise is a well-studied part of treatment.

Achilles tendon

The strongest tendon in the body, connecting the calf muscles to the heel bone. Overuse can make it painfully inflamed or cause it to rupture.

Achilles tendon reflex

A stretch reflex in which a tap on the Achilles tendon causes a brief downward extension of the foot. It mainly tests the S1 nerve root; its absence may indicate a slipped disc or polyneuropathy.

Achilles tendon rupture

A tear of the Achilles tendon, often during a sudden effort in sport and accompanied by a whip-like snapping sound. It is treated surgically or conservatively with a special boot.

Achondroplasia

The most common form of inherited short stature, with short arms and legs and a normal-length trunk, caused by a change in the FGFR3 gene. The mutation usually arises anew; intellectual development is normal.

Achromatopsia

A rare congenital retinal disease in which the cones do not work. Affected people see no colours, are very sensitive to glare and have markedly reduced visual acuity.

Aciclovir

An antiviral drug against herpes viruses, for example for cold sores or shingles.

Acidosis

Excess acidity of the blood with a pH below 7.35, for example in breathing disorders, kidney failure or uncontrolled diabetes.

Acinar cells

Gland cells in the terminal units of the pancreas that produce digestive enzymes such as lipase, amylase and trypsin. They make up most of the organ.

Acinetobacter baumannii

A hardy Gram-negative bacterium in the environment that causes serious hospital infections such as ventilator-associated pneumonia and wound infections, mainly in intensive care. It is often multidrug-resistant and a major hospital hygiene problem.

Acipimox

A nicotinic acid derivative that inhibits fat release from fatty tissue and lowers triglycerides. A benefit for cardiovascular events is not proven; flushing is common.

Acitretin

An oral retinoid used for severe psoriasis and keratinisation disorders. Because it harms the unborn child, women must use reliable contraception during and for three years after treatment.

ACL-RSI scale

A questionnaire on psychological readiness to return to sport after an anterior cruciate ligament injury, with questions on emotions, confidence and risk appraisal.

Aclidinium bromide

A long-acting inhaled anticholinergic (LAMA) that widens the airways and is used for maintenance treatment of COPD. Dry mouth is a common side effect.

ACMG classification

A five-tier scheme of the American College of Medical Genetics and Genomics for assessing genetic variants: pathogenic, likely pathogenic, uncertain significance, likely benign and benign. It is based on criteria such as population frequency, functional data and inheritance within families.

Acne

Common disorder of the sebaceous glands with blackheads, spots and inflammation, mainly on the face, chest and back. It is most frequent during puberty but can persist into adulthood.

In depth: Acne →

Acne conglobata

A severe form of acne with deep, interconnected nodules, abscesses and sinus tracts, mainly on the trunk. It often leaves marked scars and requires dermatological treatment, usually with isotretinoin.

See also: Acne

Acne fulminans

A rare, sudden-onset, very severe acne with ulcers, fever, joint pain and raised inflammatory markers, usually in young men. Paradoxically, it can also occur at the start of isotretinoin treatment.

Acne keloidalis nuchae

Chronic inflammation of hair follicles on the nape of the neck leading to hard, ridged nodules and scars. It mainly affects men with tightly curled hair; close shaving and friction can make it worse.

Acne scar treatment

Procedures to improve depressed or raised scars after acne, such as laser, microneedling, chemical peels, subcision or fillers. Several sessions are usually needed; complete smoothing is rarely achievable.

See also: Acne

Acoramidis

A stabiliser of the transport protein transthyretin that slows its breakdown into harmful amyloid fibres. It is used in transthyretin amyloidosis with heart involvement.

Acoustic neuroma

A benign tumour on the hearing and balance nerve, causing one-sided hearing loss.

Acral lentiginous melanoma

A form of melanoma on the palms, soles and under the nails that is not related to UV radiation. It is the most common melanoma type in people with dark skin and is often detected late.

Acrocyanosis

A harmless, usually constitutional bluish, cool discolouration of the hands and feet that increases in the cold. Unlike Raynaud’s phenomenon, there are no episodic colour changes.

Acrodermatitis chronica atrophicans

A late skin manifestation of Lyme disease that often begins years after the tick bite on the arms or legs with bluish-red discolouration and later leads to thin, cigarette-paper-like skin. It can be treated with antibiotics, but skin thinning that has already occurred hardly recovers.

Acrodermatitis enteropathica

An inherited disorder of zinc absorption in the gut (SLC39A4 gene) that usually appears after weaning. Typical are crusted skin inflammation around the mouth, anus, hands and feet, diarrhoea and hair loss; lifelong zinc supplementation is effective.

Acrodynia

A rare disease, mostly in children, caused by chronic mercury exposure, with painful, red, swollen hands and feet, sweating and irritability. It is also known as pink disease.

Acromegaly

A condition caused by too much growth hormone in adulthood, with enlargement of the hands, feet and facial features.

Acromion

The bony projection of the shoulder blade that forms the point of the shoulder and, with the collarbone, the acromioclavicular joint. Together with a ligament it forms the roof over the rotator cuff.

Acrophobia

Excessive fear of heights that can trigger dizziness, palpitations and panic even on ladders, bridges or balconies. It is distinct from normal unease at heights; exposure therapy, including with virtual reality, is effective.

Acrosome reaction

Release of enzymes from the cap (acrosome) of a sperm cell on contact with the egg’s outer layer. The enzymes allow it to penetrate the zona pellucida and thus enable fertilisation.

ACTH

Pituitary hormone that stimulates the adrenal cortex to produce cortisol. Measuring it helps determine whether a cortisol disorder originates in the pituitary or the adrenal gland.

See also: Cortisol, Cushing’s syndrome

ACTH stimulation test

A test in which synthetic ACTH is injected and the rise in cortisol is measured. An inadequate rise indicates adrenal insufficiency.

Actigraphy

Measurement of movement activity with a wrist-worn device over days to weeks to estimate sleep-wake patterns. It is used for sleep disorders and circadian rhythm disorders.

Actin

A structural protein that forms thin filaments in muscle cells and enables contraction together with myosin. In all body cells it is also part of the cytoskeleton and involved in cell movement.

Actinic keratosis

Rough, scaly skin patches on sun-exposed areas after years of UV exposure; a precursor of non-melanoma skin cancer.

In depth: Actinic Keratosis →

Actinomyces israelii

A filamentous anaerobic bacterium of the normal oral flora and the most common cause of actinomycosis. After injuries or dental procedures it can form hard, draining inflammation of the jaw.

Actinomycosis

A chronic bacterial infection caused by actinomycetes, often in the jaw and neck area. Hard swellings with draining sinuses are typical; treatment requires prolonged antibiotics.

Action potential

A brief, self-propagating electrical impulse along the membrane of nerve and muscle cells. It arises from the opening of sodium and potassium channels and transmits signals.

Activated charcoal

Finely ground, very porous charcoal that binds certain poisons and medicines in the gut. It is given in selected poisonings soon after ingestion but does not work for all substances, for example not for acids, alkalis or alcohol.

Activating care

A care principle in which people needing care do as much as possible themselves, guided and supported rather than fully looked after. The aim is to maintain or regain abilities and independence.

Active immunisation

Vaccination in which the immune system itself produces antibodies and memory cells in response to weakened or killed pathogens or parts of them. Protection begins after a few days to weeks but often lasts a long time.

Active surveillance

Active monitoring of a low-risk tumour, especially prostate cancer, with regular PSA tests, MRI and biopsies. Curative treatment is started only if there are signs of progression.

Active transport

Transport of substances across a cell membrane against a concentration gradient using energy, usually from ATP. An example is the sodium-potassium pump.

Activities of daily living

Basic everyday tasks such as washing, dressing, eating, using the toilet and moving around. Assessing them, for example with the Barthel index, shows the need for help in nursing, geriatrics and rehabilitation.

Acupressure

A method from traditional Chinese medicine in which specific body points are stimulated with finger pressure. There are indications of an effect for some uses such as nausea, but overall the evidence is limited.

Acupuncture

A method from traditional Chinese medicine in which fine needles are inserted at specific points on the body. Studies suggest relief for some types of pain, but for many other uses the benefit is not proven.

Acute

Starting suddenly and usually lasting a short time. The opposite of chronic.

Acute abdomen

Sudden, severe abdominal pain with a rigid belly that needs rapid medical assessment.

Acute and transient psychotic disorder

A psychosis that appears suddenly within a few days, with delusions, hallucinations or confusion, and usually resolves completely within weeks to a few months. Acute stress often precedes it.

Acute angle-closure glaucoma

A sudden, sharp rise in eye pressure caused by closure of the drainage angle. Typical are severe eye pain and headache, a red eye, blurred vision and nausea – it is an emergency.

Acute coronary syndrome

Umbrella term for the acute, life-threatening forms of coronary heart disease: unstable angina and heart attack. Chest pain lasting more than 20 minutes requires an immediate emergency call (112 in Europe).

Acute disseminated encephalomyelitis

Inflammatory demyelination of the brain and spinal cord, occurring mainly in children after infections. It is usually monophasic and often responds well to corticosteroids.

Acute eosinophilic pneumonia

An acute pneumonia with many eosinophils in the lung lavage fluid, often shortly after starting smoking or inhaling dust. It causes rapidly increasing breathlessness and responds well to corticosteroids.

Acute fatty liver of pregnancy

A rare, dangerous fatty liver in the last trimester of pregnancy with nausea, jaundice, low blood sugar and clotting disorders. Prompt delivery is the decisive treatment.

Acute generalised exanthematous pustulosis

A rare skin reaction, usually triggered by medicines such as antibiotics, in which numerous small sterile pustules appear on reddened skin within a few days, often with fever. It usually heals quickly after the trigger is stopped.

Acute intermittent porphyria

An inherited disorder of haem production in the liver in which precursors accumulate and trigger attacks of severe abdominal pain, nerve problems and psychiatric symptoms. Triggers include certain drugs, fasting, alcohol and hormonal changes.

Acute kidney injury

A sudden decline in kidney function within hours to days, seen as rising creatinine or falling urine output. Common causes are dehydration, sepsis and kidney-damaging drugs.

Acute liver failure

A rapid, severe loss of liver function in a previously healthy liver, with jaundice, clotting disorders and clouded consciousness. Common causes are paracetamol overdose, viral hepatitis and mushroom poisoning; liver transplantation is often needed.

Acute lymphoblastic leukaemia

The most common childhood cancer, in which immature lymphoid cells multiply in the bone marrow. With intensive chemotherapy most children are now cured long term.

Acute myeloid leukaemia

A rapidly progressing blood cancer in which immature blood-forming cells crowd out the bone marrow, causing anaemia, infections and bleeding. Immediate treatment is needed.

Acute phase response

The body’s systemic response to inflammation, infection or tissue damage, controlled mainly by interleukin-6. The liver produces more proteins such as CRP and fibrinogen, while albumin and transferrin fall.

Acute promyelocytic leukaemia

A special form of acute myeloid leukaemia with the translocation t(15;17) and the PML-RARA fusion gene. It often causes dangerous clotting disorders but is now usually curable with all-trans retinoic acid and arsenic trioxide.

See also: Acute myeloid leukaemia

Acute radiation syndrome

Illness after brief high-dose whole-body radiation, for example in nuclear accidents. Depending on the dose, the bone marrow, gut and nervous system are damaged; nausea soon after exposure is an early sign.

Acute retinal necrosis

A severe, rapidly progressing retinal inflammation caused by herpes viruses such as varicella-zoster or herpes simplex. It requires immediate antiviral treatment because of the risk of retinal detachment and blindness.

Acute stress reaction

A temporary, intense reaction to an exceptionally stressful event, with dazedness, anxiety, restlessness or withdrawal, usually subsiding within hours to days. If symptoms persist, a trauma-related disorder may develop.

Acute zonal occult outer retinopathy

A rare retinal disease with sudden visual field loss and flashes of light while the fundus initially looks normal. Diagnosis relies on OCT, autofluorescence and electroretinography.

Adagrasib

A targeted inhibitor of the mutated KRAS G12C variant, used in previously treated non-small cell lung cancer with this mutation. Common side effects are gastrointestinal complaints and raised liver enzymes.

Adalimumab

A TNF-alpha-blocking antibody used for chronic inflammatory conditions such as rheumatoid arthritis, psoriasis and inflammatory bowel disease.

Adamantinoma

A very rare, slow-growing malignant bone tumour found almost always in the shin bone. It is treated by complete surgical removal.

Adams-Oliver syndrome

A rare congenital malformation with skin defects on the scalp (aplasia cutis) and shortened fingers or toes. Heart or vascular malformations are sometimes present.

Adams-Stokes attack

Sudden, brief loss of consciousness because the heart beats too slowly or not at all for a few seconds due to a severe rhythm disorder (e.g. AV block). Repeated attacks usually require a pacemaker.

ADAMTS13 activity

A laboratory value for the activity of the enzyme that cleaves large von Willebrand factor molecules. A markedly reduced activity below 10 per cent practically proves thrombotic thrombocytopenic purpura.

Adapalene

A retinoid-like active ingredient in acne gels that unblocks pores and prevents new blackheads. It often irritates the skin at first.

See also: Acne

Adaptive trial

A study whose course may be adapted according to pre-specified rules based on interim results, for example by changing the sample size or dropping ineffective treatment arms.

Adductor canal

A muscular channel on the inner thigh through which the femoral artery, femoral vein and saphenous nerve pass. A nerve block is often placed here for pain relief after knee surgery.

Adductor muscles

The muscle group on the inner thigh that pulls the leg towards the midline. Adductor strains are common in ball sports.

Adductor strain

Overstretching of the muscles on the inner thigh, often during rapid changes of direction or splits-type movements. Groin pain when squeezing the legs together is typical.

Adenoid cystic carcinoma

A slow-growing but persistent malignant tumour, usually of the salivary glands, that typically spreads along nerves. Late recurrences and lung metastases are possible even after years.

Adenoidectomy

Surgical removal of enlarged adenoids, usually in children. Reasons include blocked nasal breathing, snoring and recurrent glue ear.

Adenoma

A benign tumour of glandular tissue found, for example, in the bowel, thyroid or pituitary gland. Some adenomas, such as those in the colon, can become malignant over time.

Adenomyosis

Growth of the uterine lining into the muscular wall of the uterus, causing severe period pain.

Adenosine

A natural messenger substance that, given as a rapid injection, blocks conduction in the AV node for seconds. It can stop certain episodes of racing heart (AV nodal re-entry); brief flushing and chest pressure are common.

Adenosine deaminase deficiency

An inherited enzyme defect in which toxic metabolites accumulate in lymphocytes, causing severe combined immunodeficiency (SCID). It is treated with stem cell transplantation, enzyme replacement or gene therapy.

Adenoviruses

A group of viruses that cause colds, conjunctivitis and gastrointestinal infections. Some are used as carriers in vaccines and gene therapies.

ADHD

Attention deficit hyperactivity disorder, marked by inattention, impulsivity and/or hyperactivity. It begins in childhood and often persists into adulthood.

Adherence

The extent to which patients actually follow a jointly agreed treatment, such as taking their medicines. Poor adherence is a common reason for inadequate treatment results.

Adhesiolysis

Surgical release of adhesions, for example in the abdomen after previous operations or inflammation. It is performed for bowel obstruction or chronic pain caused by adhesions, often by keyhole surgery.

Adhesion

Bands of scar tissue joining organs or tissue layers, usually after surgery or inflammation in the abdomen. They can cause pain or bowel obstruction.

Adhesive bowel obstruction

Bowel obstruction caused by bands of adhesions in the abdomen, usually after previous operations. Colicky abdominal pain, vomiting and failure to pass stool are typical.

Adhesive dentistry

Techniques that bond fillings, ceramics or brackets micromechanically and chemically to enamel and dentine. They allow tooth-sparing preparations.

Adie pupil

A usually one-sided dilated pupil that reacts only very slowly to light, often in young women and caused by damage to the ciliary ganglion. If tendon reflexes are also reduced, it is called Holmes-Adie syndrome.

Adipocyte

A fat cell that stores energy as triglycerides and releases hormones such as leptin and adiponectin. Brown fat cells can also generate heat.

Adiponectin

A hormone from fat tissue that improves insulin sensitivity and has anti-inflammatory effects. Levels are usually low in people with obesity.

Adipsia

Absent or greatly reduced sense of thirst, usually due to damage to the hypothalamus. Affected people drink too little and can develop dangerous sodium imbalances.

Adjustment disorder

A stress reaction to major life events, such as separation or job loss, that goes beyond the usual degree.

Adjuvant therapy

Additional treatment after surgery intended to lower the risk of relapse.

Adjuvant (vaccine)

An additive in vaccines that strengthens the immune response, such as aluminium salts or oil-in-water emulsions. Less antigen is then needed and protection is stronger or longer-lasting; local reactions may be more frequent.

Adolescence

The transitional phase from childhood to adulthood, involving physical maturation, identity formation and growing independence. It spans roughly from age ten into the early twenties.

Adrenalectomy

Surgical removal of an adrenal gland, often by keyhole surgery, for example for hormone-producing tumours such as phaeochromocytoma or Conn’s adenoma. After removal of both glands, lifelong hormone replacement is needed.

Adrenaline auto-injector

A pre-filled pen with which people with severe allergies can inject adrenaline into their thigh muscle during anaphylaxis. Emergency services must always be called afterwards; users should be trained regularly.

Adrenaline (epinephrine)

Stress hormone from the adrenal medulla that raises heart rate and blood pressure and mobilises energy. As an emergency drug it is given in cardiac arrest and severe allergic reactions.

Adrenarche

The increasing production of male hormone precursors by the adrenal cortex, beginning a few years before puberty proper. It shows as body odour and first pubic hair.

Adrenoleukodystrophy

A rare X-linked metabolic disease in which very-long-chain fatty acids are not broken down and damage the brain’s myelin and the adrenal cortex. In boys, early stem cell transplantation can halt progression; women are usually affected later and more mildly.

Adson test

An examination when thoracic outlet syndrome is suspected: during deep inspiration with the head turned to the affected side, the examiner checks whether the wrist pulse weakens. The test is also positive in many healthy people and is therefore of limited value.

Aducanumab

A monoclonal antibody against amyloid-beta deposits, the first of its kind to receive accelerated approval for Alzheimer’s disease in the USA. Because of disputed efficacy data and side effects such as brain swelling (ARIA), the manufacturer withdrew it in 2024.

Advance care planning

A process of conversations in which people clarify and record their wishes for future medical treatment at an early stage. It goes beyond simply completing an advance directive.

Advanced glycation end products (AGEs)

Compounds of sugars and proteins that stiffen tissue and accumulate in diabetes and ageing.

Advanced practice nurse

A nurse with a master’s degree and extended clinical competencies, for example in counselling, assessment and care coordination. In Germany the role is still being established.

Adventitia

The outermost connective tissue layer of the blood vessel wall, which anchors the vessel in its surroundings and contains small supplying vessels and nerves.

Adynamia

Marked physical weakness and lack of drive, for example in infections, adrenal insufficiency, electrolyte disorders or cancer.

AED (automated external defibrillator)

A portable device that analyses the heart rhythm itself and guides lay rescuers through delivering a shock with spoken instructions. In ventricular fibrillation, early use together with chest compressions markedly improves survival.

Aeromonas

A genus of Gram-negative bacteria from fresh and brackish water. They can cause diarrhoea and, after water-related injuries or leech therapy, severe wound infections.

Aerophagia

Excessive, usually unconscious swallowing of air, for example when eating hastily, chewing gum or under tension. Typical consequences are frequent belching, fullness and bloating.

Aerosol transmission

Transmission of pathogens via very fine particles that float in the air for a long time and can be inhaled even over larger distances and in poorly ventilated rooms. Measles, tuberculosis and SARS-CoV-2 spread this way.

Aesthetic surgery

A branch of plastic surgery with procedures that change appearance without medical necessity.

Aetiology

The study of the causes of disease; also the cause of a particular illness.

Afatinib

An irreversible inhibitor of the EGFR family taken as a tablet for non-small cell lung cancer with activating EGFR mutations. Diarrhoea, rash and nail bed inflammation are common.

Affective rigidity

A psychopathological finding in which mood hardly responds to external events and remains fixed on one feeling. It occurs, for example, in severe depression.

Afferent loop syndrome

A complication after stomach surgery with Billroth II reconstruction in which the incoming bowel loop is kinked or narrowed. Bile and pancreatic juice build up, causing abdominal pain and bilious vomiting.

Affiliated physician (Belegarzt)

A community-based doctor who treats their own patients as inpatients in a hospital on so-called affiliated beds without being employed there. The model is common mainly in smaller hospitals in Germany.

Affinity maturation

A process in the germinal centres of lymph nodes in which B cells with ever better-fitting antibodies are selected. This is why antibodies bind more strongly after repeated antigen contact, for example after booster vaccinations.

Afibrinogenaemia

A very rare, usually autosomal recessive clotting disorder in which fibrinogen is practically absent from the blood. Severe bleeding, for example from the umbilical stump, can occur; treatment is with fibrinogen concentrate.

Aficamten

A cardiac myosin inhibitor that dampens the excessive contractile force of the heart muscle. It was developed to treat symptomatic obstructive hypertrophic cardiomyopathy; its approval status varies by country.

Aflibercept

A genetically engineered fusion protein that captures VEGF and inhibits the growth of abnormal vessels. It is mainly injected into the eye for wet macular degeneration and diabetic macular oedema.

Agammaglobulinaemia

A congenital immunodeficiency in which hardly any B cells or antibodies are produced; the most common form is X-linked (Bruton’s disease). Affected children develop repeated bacterial infections from the second half of their first year and need lifelong immunoglobulins.

Agenesis

Complete absence of an organ or body part because its primordium failed to form during embryonic development, for example renal agenesis. It is distinguished from aplasia (primordium present but undeveloped) and hypoplasia (underdevelopment).

Ageusia

Complete loss of the sense of taste. Reduced taste is more common and is often actually due to a smell disorder.

Aggregatibacter actinomycetemcomitans

A Gram-negative bacterium closely associated with aggressive forms of periodontitis in young people. It can also rarely cause endocarditis and belongs to the HACEK group.

Agnosia

Inability to recognise objects, faces or sounds despite intact sense organs. It results from damage to specific brain regions, for example after stroke or in dementia.

Agomelatine

An antidepressant that activates melatonin receptors and blocks a serotonin receptor, intended to stabilise the sleep-wake rhythm. Because of possible liver damage, regular liver tests are mandatory.

Agonist

A substance that binds to a receptor and activates it in a similar way to the body’s own messenger. Partial agonists produce only part of the effect.

Agoraphobia

Fear of places or situations from which escape seems difficult, such as crowds or public transport.

Agranulocytosis

An almost complete absence of granulocytes in the blood, often a rare side effect of drugs such as metamizole or antithyroid medicines. Warning signs are fever, sore throat and mouth inflammation.

Agraphia

Acquired inability to write despite intact hand movement. It often occurs together with aphasia or alexia after brain damage.

Aicardi-Goutières syndrome

A rare inherited encephalopathy in which a misdirected interferon response causes brain damage, calcifications and developmental regression in infancy. It is one of the interferonopathies and clinically resembles a congenital viral infection.

Aicardi syndrome

A very rare developmental disorder occurring almost only in girls, with absent or incomplete corpus callosum, typical retinal changes (lacunae) and early-onset epileptic seizures. Treatment is supportive and focuses mainly on seizure control.

Air bronchogram

Visible air-filled bronchi within a consolidated area of lung on X-ray or CT. It indicates that the air sacs rather than the bronchi are filled, for example in pneumonia.

Airway resistance

The resistance the airways offer to airflow, determined mainly by the diameter of the bronchi. It is raised in asthma and COPD and measured by body plethysmography.

Ajmaline

A class Ia antiarrhythmic given intravenously. It is used mainly as a provocation test to diagnose Brugada syndrome and only under monitoring.

Akathisia

Distressing inner restlessness with an urge to move, so that sitting still is hardly possible. It occurs mainly as a side effect of antipsychotics.

Akin osteotomy

A wedge-shaped removal of bone from the base of the big toe to correct remaining misalignment. It is usually done in addition to a metatarsal osteotomy for hallux valgus.

Akinetic mutism

A state in which an awake person makes almost no spontaneous movements and does not speak, although there is no paralysis. It is caused by damage to frontal or diencephalic regions that control drive and initiation of action.

Akinetopsia

A very rare disorder in which movement is no longer perceived as fluid but as a sequence of still images. It is caused by damage to cortical area V5, which is responsible for motion vision.

Akkermansia muciniphila

A gut bacterium that feeds on the mucus of the intestinal wall and helps renew the mucus layer. Low levels are linked to obesity and metabolic disorders; whether supplementation helps is not yet sufficiently proven.

AL amyloidosis

Amyloidosis in which misfolded antibody light chains from an abnormal plasma cell clone are deposited in organs, especially the heart and kidneys. Treatment targets the plasma cells.

Alagille syndrome

An inherited multisystem disease with too few bile ducts in the liver, chronic bile congestion and itching. Other features are heart defects, butterfly vertebrae and a typical facial appearance; it is usually caused by JAG1 variants.

Albendazole

A broad-spectrum anthelmintic that inhibits glucose uptake by parasites. It is used for roundworms and hookworms and as supportive therapy in echinococcosis and neurocysticercosis.

Albinism

A congenital disorder of melanin production with pale skin, light hair and often impaired vision. Consistent sun protection is important.

Albumin

The most abundant protein in blood plasma, made by the liver. It keeps fluid inside the blood vessels and transports hormones, fatty acids and medicines.

Albumin-to-creatinine ratio

A urine value showing albumin excretion relative to creatinine. It is used mainly in diabetes and hypertension to detect kidney damage early.

Alcohol consumption

Drinking alcoholic beverages; according to current knowledge there is no amount that is entirely without health risk.

Alcohol dependence

Addiction with loss of control over drinking and withdrawal symptoms. It is treatable, for example with detoxification, rehabilitation and self-help groups.

Alcohol poisoning

Acute intoxication after consuming large amounts of alcohol, with unsteadiness, vomiting and clouded consciousness up to respiratory failure. Unconsciousness requires an emergency call.

Alcoholic hepatitis

Acute inflammation of the liver, usually after many years of heavy drinking, with jaundice, fever and an enlarged, tender liver. Severe cases have high short-term mortality; alcohol abstinence, nutrition and, in selected cases, corticosteroids are central.

Aldosterone

An adrenal hormone that regulates salt and water balance and therefore blood pressure.

Aldosterone-to-renin ratio

A screening test for primary hyperaldosteronism that measures the ratio of aldosterone to renin in the blood. Many blood pressure medicines influence the result.

See also: Aldosterone, Conn’s syndrome

Aldrete score

A scoring system used in the recovery room that assesses movement, breathing, circulation, consciousness and oxygen saturation. It helps decide when a patient can be transferred to the ward.

Alectinib

An ALK tyrosine kinase inhibitor for ALK-positive non-small cell lung cancer. It also works well against brain metastases because it crosses the blood-brain barrier.

Alemtuzumab

A monoclonal antibody against the surface marker CD52 that strongly depletes lymphocytes. It is used in highly active relapsing multiple sclerosis; important risks are autoimmune diseases, infections and infusion reactions.

Alendronic acid

A widely used bisphosphonate for osteoporosis, usually taken as a weekly tablet. It is taken in the morning on an empty stomach with tap water, staying upright for at least 30 minutes afterwards.

Alexander disease

A rare inherited leukodystrophy caused by mutations in the GFAP gene, in which abnormal protein deposits form in astrocytes and the brain’s white matter is damaged. The infantile form often shows an enlarged head, developmental regression and seizures.

Alexia

Acquired loss of the ability to read in previously literate people, usually after a stroke in the posterior part of the dominant hemisphere. In pure alexia, writing is preserved.

Alexithymia

A personality trait in which people find it difficult to perceive, distinguish and put their own feelings into words. It is not a diagnosis in itself but is more common in psychosomatic complaints.

Alfacalcidol

A precursor of active vitamin D that only needs conversion in the liver and therefore works in impaired kidney function. It is used, for example, in renal bone disease and underactive parathyroid glands; calcium levels are monitored regularly.

Alfentanil

A potent, very short-acting opioid used in anaesthesia for brief procedures and to blunt stress responses. Like all opioids, it can suppress breathing.

Alfuzosin

An alpha-1 receptor blocker that relaxes the muscles of the prostate and bladder neck, making urination easier in benign prostate enlargement. Common side effects are dizziness and a drop in blood pressure on standing.

Alginate dressing

A wound dressing made of seaweed fibres that absorbs a lot of exudate and forms a moist gel. It is suitable for heavily exuding and deep wounds and has a mild haemostatic effect.

Alice in Wonderland syndrome

A perceptual disorder in which one’s own body or objects appear distorted, too large or too small. It occurs mainly in children with migraine or Epstein-Barr virus infection and is usually harmless.

Alien hand syndrome

A disorder in which one hand seems to act independently and involuntarily, for example grasping objects or working against the other hand. Causes are damage to the corpus callosum or frontal lobe, for example in corticobasal degeneration.

ALIF (anterior lumbar interbody fusion)

Fusion of lumbar vertebrae through an approach from the front via the abdomen. It allows large implants but carries vascular and abdominal risks.

Aligners

Clear, removable plastic trays that gradually straighten teeth.

In depth: Aligners →

Alimemazine

An older, strongly sedating phenothiazine antihistamine used mainly for restlessness and sleep problems. Caution is needed in older people because of anticholinergic side effects.

Aliskiren

A blood pressure medicine that directly inhibits the enzyme renin and thus acts early in the renin-angiotensin-aldosterone system. It is rarely used today; combination with ACE inhibitors or sartans is not recommended in diabetes or kidney impairment.

Alitretinoin

An oral retinoid for severe chronic hand eczema that does not respond to corticosteroid creams. Because it harms the foetus, a strict pregnancy prevention programme applies.

Alizapride

A dopamine antagonist against nausea and vomiting, chemically related to metoclopramide. It has been used mainly for chemotherapy-induced nausea; movement disorders are possible side effects.

ALK rearrangement

A gene rearrangement in which the ALK gene fuses with another gene, creating a permanently active growth signal. It is found in a small proportion of non-small cell lung cancers and can be treated specifically with ALK inhibitors such as alectinib.

Alkaline phosphatase

An enzyme from the liver, bile ducts and bone; raised, for example, in bile congestion or increased bone turnover.

Alkalosis

A rise in blood pH above 7.45, for example from over-breathing or heavy acid loss through vomiting. It can cause tingling, muscle cramps and heart rhythm disturbances.

Alkaptonuria

A rare metabolic disorder in which homogentisic acid accumulates, turning urine dark on standing and damaging cartilage.

All-on-4 implant

A concept for fixed dentures in a toothless jaw, with a bridge anchored on four implants, the back ones often placed at an angle. Long-term results depend greatly on bone availability and care.

All-or-nothing principle

The principle that an action potential is either triggered completely once the threshold is reached or not at all. The strength of a stimulus is therefore encoded by the frequency of action potentials, not their size.

Allantois

An embryonic outpouching of the hindgut whose vessels form the umbilical cord vessels. Its remnant becomes the urachus, a fibrous cord between the bladder and the navel.

Allele

A variant form of a gene; for most genes each person has two alleles, one from the mother and one from the father.

Allen test

A simple test before puncturing or cannulating the radial artery that checks whether the hand is adequately supplied by the ulnar artery. Both arteries are compressed and reperfusion of the palm is observed after releasing the ulnar artery.

Allergic bronchopulmonary aspergillosis

A hypersensitivity reaction of the airways to the mould Aspergillus, mainly in asthma or cystic fibrosis. Typical are poorly controlled asthma, thick mucus, bronchiectasis and very high IgE; treatment is with corticosteroids and sometimes antifungals.

Allergology

The specialty concerned with diagnosing and treating allergic diseases such as hay fever and insect venom or food allergies.

Allergy

An exaggerated immune reaction to normally harmless substances (allergens) such as pollen, house dust mites or foods. Symptoms range from sneezing and itching to life-threatening anaphylaxis.

Allergy passport

A document in which medically confirmed allergies, for example to medicines, insect venom or contrast media, are recorded. It should always be carried and shown at every treatment.

Allodynia

Pain caused by stimuli that are not normally painful, such as light touch. It is typical of nerve pain and migraine.

Allogeneic stem cell transplantation

Transfer of blood stem cells from a matched donor after preparatory conditioning. The donor’s immune cells can fight remaining leukaemia cells but can also cause graft-versus-host disease.

Allopurinol

A medicine that inhibits uric acid production and helps prevent gout attacks.

Almotriptan

A triptan migraine medicine that narrows blood vessels in the head and inhibits the release of inflammatory messengers. It is taken at the start of the headache phase and is unsuitable in cardiovascular disease.

Aloe vera

A plant whose leaf gel is used in care products for irritated or sun-stressed skin. Its main effects are cooling and moisturising.

Alogliptin

A DPP-4 inhibitor that lowers blood sugar in type 2 diabetes by enhancing the body’s own incretin effect. On its own it rarely causes hypoglycaemia and is weight-neutral.

Alopecia

Hair loss. Common forms are hereditary-hormonal (androgenetic) hair loss and patchy hair loss (alopecia areata).

Alopecia mucinosa

Hairless, slightly raised patches caused by mucin deposits in the hair follicles. In adults it can be associated with cutaneous T-cell lymphoma and should be examined histologically.

Alpelisib

A PI3K-alpha inhibitor used with fulvestrant in hormone-receptor-positive, HER2-negative breast cancer with a PIK3CA mutation. Common side effects are raised blood sugar, diarrhoea and rash.

Alpers-Huttenlocher syndrome

A rare mitochondrial disease caused by mutations in the POLG gene, with drug-resistant epilepsy, developmental regression and liver failure. Valproic acid is contraindicated because it can trigger liver failure.

Alpha-1 antitrypsin deficiency

An inherited disorder in which a protective protein is missing; it can lead to early emphysema and liver damage.

Alpha-1 microglobulin

A small protein that is normally almost completely reabsorbed by the kidney tubules. Increased excretion in the urine indicates damage to the renal tubules.

Alpha-2 antiplasmin

A blood protein that rapidly inhibits plasmin and so prevents excessive clot breakdown. Inherited deficiency can lead to a bleeding tendency.

Alpha blockers

Medicines that block alpha-1 receptors, relaxing blood vessels and the muscles of the prostate and bladder neck. They are used for benign prostate enlargement and as a reserve option in hypertension; dizziness on standing is typical.

Alpha cell

A glucagon-producing cell in the islets of Langerhans of the pancreas. Glucagon is released when blood sugar is low and stimulates the liver to release glucose.

Alpha-fetoprotein

A protein produced by the unborn baby; in adults its blood level serves as a tumour marker for liver cancer and germ cell tumours. In pregnancy it is sometimes measured as part of prenatal testing.

Alpha-gal syndrome

A delayed allergic reaction to the sugar molecule galactose-alpha-1,3-galactose, found in mammalian meat and offal and in gelatine; symptoms typically start only three to six hours after eating. It is often triggered by tick bites.

Alpha-mannosidosis

A rare inherited lysosomal storage disease with hearing loss, intellectual disability, skeletal changes and susceptibility to infections. Enzyme replacement therapy is available for some patients.

Alpha motor neuron

A large nerve cell in the anterior horn of the spinal cord or in cranial nerve nuclei that directly controls the working muscle fibres. Its loss, for example in ALS or spinal muscular atrophy, leads to flaccid paralysis.

Alport syndrome

An inherited disease caused by altered collagen in basement membranes, affecting mainly the kidneys, inner ear and eyes. Typical are blood in the urine, progressive kidney failure and hearing loss.

Alprazolam

A short- to intermediate-acting benzodiazepine used mainly for panic disorder and anxiety. It has a high dependence potential; it must be stopped slowly to avoid withdrawal symptoms and seizures.

Alprostadil

A synthetic prostaglandin E1 that widens blood vessels. It is used in newborns to keep the ductus arteriosus open in certain heart defects, and as an injection or urethral pellet for erectile dysfunction; side effects include pain at the application site.

Alström syndrome

A very rare autosomal recessive ciliopathy with early retinal degeneration, hearing loss, obesity, insulin resistance and often heart muscle weakness in infancy. It is caused by mutations in the ALMS1 gene.

Altemeier procedure

Removal of the prolapsed rectal and sigmoid segment through the anus in full-thickness rectal prolapse. Because it is less demanding on the body, it is particularly suitable for older or frail people.

Alteplase

A genetically engineered tissue plasminogen activator that dissolves blood clots (thrombolysis). It is given within narrow time windows for acute stroke and severe pulmonary embolism.

Alternative hypothesis

In a statistical test, the counter-assumption to the null hypothesis, for example that two treatments really differ. It is accepted when the data refute the null hypothesis at the chosen significance level.

Alvarado score

A ten-point score based on symptoms, examination findings and laboratory values that estimates the probability of appendicitis.

Alveolar-arterial oxygen gradient

The difference between the oxygen partial pressure in the air sacs and in arterial blood. A raised value points to diffusion problems, shunts or ventilation-perfusion mismatch.

Alveolar bone

The part of the jawbone that forms the tooth sockets and holds the teeth. After tooth loss it gradually recedes.

Alveolar echinococcosis

Infection with the larvae of the fox tapeworm, which grow into the liver like a tumour. It progresses insidiously over years; treatment is surgery and usually long-term albendazole.

Alveolar macrophages

Scavenger cells in the air sacs that take up and break down inhaled particles, dust and pathogens. They are an important first line of defence of the lung and regulate inflammatory responses.

Alveolar ventilation

The part of the air inhaled per minute that actually reaches the air sacs and takes part in gas exchange; the rest only fills the dead space. Shallow, rapid breathing is therefore inefficient; alveolar ventilation determines the CO2 level in the blood.

Alveoli

Tiny, thin-walled air sacs at the end of the airways where oxygen passes into the blood and carbon dioxide is released.

Alveolitis

Inflammation of the air sacs of the lung, often an allergic reaction to inhaled organic dusts such as mould or bird droppings. Untreated, it can progress to lung fibrosis.

Alvimopan

An opioid receptor antagonist acting only in the gut, intended to speed recovery of bowel function after bowel surgery. It is approved in the USA, where it is subject to strict conditions.

Alzheimer’s disease

The most common form of dementia. Protein deposits (amyloid plaques and tau tangles) cause progressive loss of brain nerve cells, so memory, orientation and everyday skills decline.

Amantadine

A drug originally developed against influenza viruses and now used mainly in Parkinson’s disease, as it can reduce involuntary movements (dyskinesias). It blocks NMDA receptors, among others, and is excreted by the kidneys.

Amaurosis fugax

Sudden, temporary loss of vision in one eye for seconds to minutes, usually from a small embolus from the carotid artery. It is a warning sign of stroke and needs prompt assessment.

Ambivalence

The simultaneous existence of opposing feelings, wishes or intentions towards the same person or thing. In a pronounced form that paralyses decisions, Eugen Bleuler described it as a fundamental symptom of schizophrenia.

Amblyopia

Reduced vision in one eye that develops in childhood, for example due to a squint; often well correctable if treated early.

Ambrisentan

A selective endothelin A receptor antagonist taken as tablets for pulmonary arterial hypertension, often combined with tadalafil. It can harm the unborn child, so reliable contraception is required.

Ambroxol

A mucolytic for coughs with thick sputum; as a lozenge it also has a local anaesthetic effect on sore throats. Severe allergic skin reactions are rare.

Ameloblastoma

A usually benign but locally aggressive jaw tumour arising from tooth-forming tissue, mainly in the lower jaw. Because it tends to recur, it is removed with a safety margin.

Ameloblasts

Cells that form tooth enamel during tooth development and die after the tooth erupts. This is why lost enamel cannot grow back.

Amelogenesis imperfecta

An inherited disorder of tooth enamel formation in which enamel is too thin, too soft or discoloured. Affected teeth are sensitive and wear quickly; crowns are often needed.

Amenorrhoea

Absence of menstrual periods, for example due to pregnancy, marked weight loss or hormonal disorders.

Amifampridine

A drug that blocks potassium channels at nerve endings and thereby increases acetylcholine release. It is used in Lambert-Eaton syndrome to improve muscle strength; tingling around the mouth is common.

Amifostine

A cytoprotective agent intended to protect healthy tissue from damage by radiotherapy or platinum chemotherapy, for example the salivary glands during head and neck radiation. Because of low blood pressure and nausea it is now used rather rarely.

Amikacin

An aminoglycoside antibiotic for severe Gram-negative infections and multidrug-resistant tuberculosis; inhaled, also for lung infections with non-tuberculous mycobacteria. Because of possible kidney and inner ear damage, blood levels are monitored.

Amiloride

A potassium-sparing diuretic that blocks sodium channels in the kidney’s collecting duct and is usually combined with a thiazide. It is specifically effective in Liddle syndrome; potassium is monitored because of the risk of hyperkalaemia.

Aminocaproic acid

An antifibrinolytic that, like tranexamic acid, inhibits the breakdown of blood clots. In Germany the more potent tranexamic acid is mainly used today.

Aminoglycosides

A group of antibiotics, such as gentamicin, that act mainly against Gram-negative bacteria. Because they can damage the kidneys and inner ear, blood levels are monitored.

Aminophylline

A water-soluble compound of theophylline that widens the airways and can be given intravenously. Because of its narrow therapeutic range, blood levels must be monitored; in acute asthma it is now only a reserve option.

Amiodarone

A highly effective antiarrhythmic drug that can, however, affect the thyroid, lungs, liver, skin and eyes. Because of its long half-life, its effect persists long after stopping.

Amisulpride

A benzamide antipsychotic that selectively blocks dopamine D2/D3 receptors and is used in schizophrenia. Typical side effects are raised prolactin and QT prolongation.

Amitriptyline

An older tricyclic antidepressant that is also used at low doses to prevent chronic pain and tension-type headache. Typical side effects are dry mouth, drowsiness and weight gain.

Amivantamab

A bispecific antibody against EGFR and MET used in non-small cell lung cancer with EGFR mutations such as exon 20 insertions. Infusion reactions, rashes and nail inflammation are common.

Amlodipine

A calcium channel blocker used to lower blood pressure; swollen ankles are a common side effect.

Ammonia

A toxic breakdown product of protein metabolism that is normally converted to urea in the liver. In severe liver damage it rises and can affect the brain.

Amnesia

Loss of memory in which recollections of a period are missing or new information cannot be stored, for example after concussion.

Amniocentesis

Sampling of amniotic fluid by needle to reliably detect genetic changes in the baby.

Amnion

The innermost foetal membrane that surrounds the embryo and produces the amniotic fluid. Together with the chorion it forms the amniotic sac.

AMNOG (German drug benefit assessment)

A German law of 2011 under which new medicines undergo an early benefit assessment after approval. The result determines the price reimbursed by health insurers.

Amoebic dysentery

Intestinal infection with the single-celled parasite Entamoeba histolytica, transmitted through contaminated water or food in warm countries. Typical are bloody, mucous diarrhoea; rarely a liver abscess develops.

Amok

A sudden outburst of extreme, often lethal violence against several people, originally described as a culture-bound syndrome from Southeast Asia. Grievances, withdrawal and mental illness often precede it.

Amorolfine

An antifungal applied as nail lacquer for mild to moderate nail fungus. Treatment must be continued consistently for many months until the nail has grown out healthy.

Amoxicillin

A broad-spectrum antibiotic of the penicillin group, often used for middle ear, respiratory and urinary tract infections.

Amphetamine intoxication

Poisoning by amphetamines, methamphetamine or ecstasy with agitation, racing heart, overheating and sometimes psychotic symptoms. With ecstasy, dangerous hyponatraemia can also occur.

Amphotericin B

An old, very broad-spectrum antifungal that punches holes in fungal cell membranes. It is given by infusion for severe systemic fungal infections, nowadays mostly in liposomal form to reduce kidney damage.

Ampicillin

An aminopenicillin given by infusion against, for example, enterococci and listeria, often combined with the beta-lactamase inhibitor sulbactam. In glandular fever a rash often develops on ampicillin, which need not be a true allergy.

Ampulla of Vater

A small widening where the common bile duct and pancreatic duct join just before entering the duodenum. A gallstone lodged here can cause bile congestion and pancreatitis.

Ampullary tumour

A tumour of the papilla of Vater, where the bile and pancreatic ducts open into the duodenum. It often presents early with painless jaundice and can be benign (adenoma) or malignant.

Amputation

Surgical removal of a body part, for example in severe circulatory disorders.

Amsacrine

A topoisomerase II inhibitor used mainly in acute myeloid leukaemia. Besides blood count changes it can trigger heart rhythm disturbances, especially with low potassium.

See also: Acute myeloid leukaemia

Amsel criteria

Clinical criteria for bacterial vaginosis: thin greyish-white discharge, pH above 4.5, fishy odour after adding potassium hydroxide and clue cells under the microscope. Three of the four criteria are considered sufficient.

Amsler grid

A checked test chart with a central dot used to detect distortions or gaps in the central visual field. People with age-related macular degeneration can use it at home to notice changes early.

Amycretin

An experimental drug that, as a single molecule, acts on both the GLP-1 and the amylin receptor and is being studied for weight loss as a tablet and an injection.

Amygdala

An almond-shaped cluster of nuclei in the temporal lobe that evaluates emotions, especially fear, and shapes emotional memories. It works closely with the hippocampus.

Amylase

A starch-digesting enzyme from the pancreas and salivary glands; raised, for example, in pancreatitis.

Amyloidosis

A group of diseases in which misfolded proteins are deposited as insoluble fibres in organs such as the heart, kidneys or nerves. Treatment depends on the type of protein deposited.

Amyotrophic lateral sclerosis (ALS)

A progressive disease in which the nerve cells that control the muscles die, leading to paralysis.

Anabolic steroids

Substances derived from testosterone that promote muscle growth and are banned in sport as doping. Misuse can cause heart and liver damage, infertility, acne, mood swings and virilisation in women.

Anaemia

Too little red blood pigment (haemoglobin) or too few red blood cells, causing tiredness, pallor and breathlessness on exertion. Iron deficiency is the most common cause.

Anaerobes

Bacteria that live and multiply without oxygen, such as clostridia or Bacteroides. They typically cause abscesses and infections in poorly perfused tissue.

Anaesthesia

Switching off pain sensation for procedures. General anaesthesia is distinguished from regional and local anaesthesia, which numb only part of the body.

Anaesthesia technician

A health profession that prepares anaesthesia, assists with induction and monitoring and supports the recovery phase. Training takes three years in Germany.

Anaesthesiology

The medical specialty that provides general and regional anaesthesia and monitors patients before, during and after surgery. It also covers intensive care, emergency medicine and pain management.

Anagen effluvium

Rapid, marked loss of growing hairs due to a sudden disturbance of the hair root, especially during chemotherapy. The hair usually grows back after treatment ends.

Anagen phase

The growth phase of the hair cycle, which can last several years on the scalp. Normally about 85 to 90 per cent of scalp hairs are in this phase at any one time.

Anagrelide

A drug that inhibits platelet production in the bone marrow and is used in essential thrombocythaemia. Common side effects are headache, palpitations and fluid retention.

Anakinra

A biotechnologically produced interleukin-1 receptor blocker injected under the skin daily. It is used, among others, for rheumatoid arthritis, Still’s disease and hereditary fever syndromes.

Anal abscess

A purulent inflammation next to the anus, usually arising from an inflamed anal gland. Severe, throbbing pain is typical; treatment is surgical drainage.

Anal atresia

Congenital absence or closure of the anal opening, often with fistulas to the urinary tract or vagina. It is detected at the newborn examination and corrected surgically.

Anal canal

The last section of the bowel, about four centimetres long, between the rectum and the anus. It contains the internal and external sphincters and vascular cushions that help seal it.

Anal cancer

A rare malignant tumour of the anal canal, usually caused by human papillomaviruses. It is often treated with combined radiotherapy and chemotherapy.

Anal fissure

A painful lengthwise tear in the skin of the anal canal, usually caused by hard stools or straining. Typical are sharp pain during and after bowel movements and bright red blood; soft stools and ointments often help, while chronic fissures may need surgery.

Anal fistula

An abnormal channel between the anal canal and the skin around the anus, usually arising from an abscess. Typical are discharge and recurrent inflammation; treatment is usually surgical.

Anal reflex

A superficial reflex in which stroking the skin around the anus causes a visible contraction of the external sphincter. Its absence may indicate damage to the sacral segments S3 to S5, for example in cauda equina syndrome.

Analgesic

Painkiller. A distinction is made between non-opioid analgesics such as ibuprofen or paracetamol and opioids such as morphine.

Analgesic nephropathy

Kidney damage from years of taking large amounts of painkillers, formerly mainly combination products. It leads to papillary necrosis and chronic kidney failure.

Analgosedation

A combination of painkillers and sedatives that keeps patients pain-free and relaxed during procedures or in intensive care without full anaesthesia. Breathing and circulation are monitored.

Anaphylaxis

The most severe form of allergic reaction, affecting several organs within minutes: breathing difficulty, a drop in blood pressure and rash, up to circulatory shock. This is an emergency – use an adrenaline auto-injector if available and call emergency services (112 in Europe).

Anaplasia

Loss of the typical cell features and organisation of a tissue, so that tumour cells barely resemble their tissue of origin. Highly anaplastic tumours usually grow particularly aggressively.

Anaplasmosis

A tick-borne bacterial infection with Anaplasma phagocytophilum that affects white blood cells. Flu-like fever, headache and muscle pain and low platelet and white cell counts are typical.

Anaplastic thyroid cancer

A rare, very aggressive thyroid cancer of older people that grows rapidly and causes breathing or swallowing difficulties. Targeted therapies are available for certain genetic changes such as BRAF V600E.

Anasarca

Marked, generalised accumulation of fluid in the subcutaneous tissue of the whole body, for example in severe heart, kidney or liver failure or severe protein deficiency.

Anastomosis

A surgically created connection between two hollow organs or vessels, for example after removal of a bowel segment. Leakage of the join is a feared complication.

Anastomotic leak

A leak in a surgically created connection, for example between two bowel segments. Escaping bowel contents can cause peritonitis; fever and abdominal pain after surgery are warning signs.

Anatomy

The study of the structure of the human body, its organs and tissues and how they lie in relation to each other. It includes gross anatomy, histology and embryology and is a core subject of medical school.

ANCA

Antibodies against components of neutrophil granulocytes that can be detected in the blood. They help diagnose certain forms of vasculitis; PR3-ANCA is typical of granulomatosis with polyangiitis, MPO-ANCA of microscopic polyangiitis.

Ancylostoma duodenale

A hookworm whose larvae penetrate the skin from moist soil and attach in the small intestine. Through constant blood loss they can cause iron deficiency anaemia.

Andersen disease

Glycogen storage disease type IV, caused by deficiency of the glycogen branching enzyme, which results in abnormally structured glycogen. The classic form leads to liver cirrhosis in early childhood.

Andersen-Tawil syndrome

A rare inherited channel disorder (KCNJ2 gene) combining periodic muscle paralysis, heart rhythm disorders and minor physical features such as short stature or low-set ears.

Anderson-D’Alonzo classification

A classification of fractures of the dens of the axis into three types by the level of the fracture line: tip, base or extending into the vertebral body. Type II fractures heal worst.

Andexanet alfa

A genetically engineered protein that can reverse the effect of the factor Xa inhibitors apixaban and rivaroxaban. It is used for life-threatening bleeding.

Androgen insensitivity syndrome

Inherited insensitivity of body cells to male hormones due to changes in the androgen receptor. People with XY chromosomes develop female or ambiguous external genitalia depending on severity.

Androgenetic alopecia

The most common form of hair loss, hereditary and influenced by androgens: receding temples and crown thinning in men, thinning at the parting in women. Medicines such as minoxidil can slow progression but only work with continued use.

Andrology

The medical field of men’s health, for example fertility and hormonal disorders.

Androstenedione

A sex hormone precursor produced in the adrenal glands and gonads and converted in tissues to testosterone or oestrogen. Raised levels are found, for example, in PCOS or congenital adrenal hyperplasia.

Anencephaly

A severe neural tube defect in which the cerebrum and skull vault are missing. The babies cannot survive; adequate folic acid intake before and in early pregnancy lowers the risk.

Anetoderma

Circumscribed skin areas where elastic fibres have been lost, so the skin bulges out like a pouch. It can arise after inflammation or without an apparent cause.

Aneurysm

An abnormal, sac-like bulge in an artery wall, often in the abdominal aorta or brain arteries. The danger lies in rupture with life-threatening bleeding.

Aneurysmal bone cyst

A benign, blood-filled bone cyst that expands and weakens the bone, mostly in children and adolescents. It can cause pain and fractures and is curetted or treated by sclerotherapy.

Angelman syndrome

A rare genetic developmental disorder caused by loss of function of a maternal gene on chromosome 15. Typical features are marked speech delay, movement problems, epilepsy and a strikingly happy demeanour.

Angina pectoris

Pressing chest pain behind the breastbone because the heart muscle temporarily receives too little oxygen. The main cause is narrowed coronary arteries (coronary heart disease).

Angiodysplasia

Dilated, fragile blood vessels in the bowel wall that can cause chronic bleeding and anaemia, especially in older people. They are treated endoscopically.

Angioedema

Sudden, deep swelling of the skin or mucous membranes, often of the lips, eyelids or tongue. Causes include allergies, drugs such as ACE inhibitors and inherited disorders; swelling in the throat is an emergency.

Angiography

Imaging of blood vessels with contrast medium using X-ray, CT or MRI.

Angiokeratoma

A small dark red to blackish papule of dilated blood vessels with a thickened horny layer. Many angiokeratomas in the swimsuit area can indicate Fabry disease.

Angiology

The internal medicine specialty for diseases of the arteries, veins and lymph vessels, such as peripheral arterial disease, thrombosis or vasculitis. Vascular ultrasound is the key examination.

Angiolymphoid hyperplasia with eosinophilia

A benign vascular proliferation with reddish nodules, usually on the head and especially around the ear, often with many eosinophils in the tissue. The nodules tend to recur after removal.

Angiosarcoma

A rare, aggressive malignant tumour of blood or lymph vessels, often on the scalp of older people or after radiotherapy. It appears as bluish-red patches or nodules.

Angiostrongyliasis

Infection with the rat lungworm Angiostrongylus cantonensis, usually from raw snails or contaminated vegetables in tropical regions. The larvae cause eosinophilic meningitis with headache and abnormal sensations.

Angiotensin II

The active hormone of the renin-angiotensin system, which constricts blood vessels and increases aldosterone release and thirst. ACE inhibitors and sartans lower blood pressure by blocking its formation or action.

Angle classification

A classification of the bite based on the relative position of the first molars: class I (neutral), class II (lower jaw too far back) and class III (lower jaw too far forward). It is a basis of orthodontic diagnosis.

Angular artery

The terminal branch of the facial artery running beside the nose to the inner corner of the eye. When filling the nasolabial fold there is a risk of vascular occlusion and tissue damage here.

Anhedonia

Loss of the ability to feel pleasure or interest in things that are normally enjoyable. It is a core symptom of depression.

Anhidrosis

Absent or greatly reduced sweating, congenital or due to nerve damage or medicines. Because heat loss is impaired, there is a higher risk of overheating in hot conditions.

Anidulafungin

An echinocandin antifungal that inhibits fungal cell wall synthesis. It is given by infusion for invasive Candida infections and is not metabolised by the liver.

Anifrolumab

An antibody that blocks the receptor for type I interferons, given by infusion for moderate to severe systemic lupus erythematosus. Shingles and respiratory infections occur more often.

Anion gap

A calculated value (sodium minus chloride and bicarbonate) that helps identify the cause of acidosis. A raised anion gap suggests, for example, lactate, ketones or poisoning.

Aniridia

Congenital, almost complete absence of the iris, usually due to changes in the PAX6 gene. Affected people are very sensitive to glare and often have other eye problems such as glaucoma, cataract or corneal clouding.

Anisakiasis

Infection with herring worm larvae after eating raw or undercooked sea fish. It causes sudden severe abdominal pain and can trigger allergic reactions; deep-freezing or thorough cooking kills the larvae.

Aniseikonia

Unequal image size on the two retinas, for example due to very different spectacle lenses or after eye surgery. It can cause double vision, headaches and problems with depth perception; contact lenses often help.

Anismus

Failure of the pelvic floor to relax, or paradoxical tensing, when straining, leading to constipation. Biofeedback training is the most effective treatment.

Anisocoria

Pupils of unequal size. A slight difference is often harmless; new anisocoria with other symptoms needs prompt assessment.

Anisocytosis

Unequal size of red blood cells on a blood smear, measurable as a raised RDW. It occurs, for example, in iron or vitamin B12 deficiency.

Anisometropia

A difference in refractive power between the two eyes, so each needs a different lens strength. In children, if untreated, it can lead to amblyopia in the weaker eye.

Ankylosis

Complete stiffening of a joint through bony or fibrous bridging, for example in ankylosing spondylitis.

Ann Arbor classification

A staging system for lymphomas based on the number and location of affected lymph node regions (stage I to IV). The suffix B indicates fever, night sweats or weight loss.

Annulus fibrosus

The outer fibrous ring of the intervertebral disc, made of several layers of fibrocartilage surrounding the gel-like nucleus. Tears in this ring are a prerequisite for a slipped disc.

Anodontia

Complete congenital absence of all teeth of one or both dentitions. It is very rare, usually part of an ectodermal dysplasia, and requires early removable dentures and later possibly implants.

Anorexia nervosa

An eating disorder with marked underweight and fear of gaining weight; early help is crucial.

Anosognosia

Inability to recognise one’s own illness or disability, such as one-sided paralysis after stroke. It results from brain damage, usually of the right hemisphere, and is not conscious denial.

Ansa cervicalis

A nerve loop in the neck formed by fibres of the upper cervical nerves (C1–C3) that supplies the infrahyoid muscles. Surgeons use it as a landmark in neck operations.

Antacids

Non-prescription remedies that chemically neutralise excess stomach acid and can quickly relieve occasional heartburn. They act briefly and can interfere with the absorption of other medicines.

Antagonist

A substance that binds to a receptor without activating it, thereby blocking the effect of natural messengers or other drugs. Examples are beta blockers and the opioid antidote naloxone.

Anterior cerebral artery

The artery from the internal carotid that supplies the inner surfaces of the frontal and parietal lobes. Its occlusion typically causes leg-dominant paralysis on the opposite side and reduced drive.

Anterior choroidal artery

A thin artery from the internal carotid that supplies parts of the internal capsule, the optic tract and the choroid plexus, among others. Its occlusion can cause one-sided paralysis, sensory loss and visual field loss.

Anterior communicating artery

A short connecting vessel between the two anterior cerebral arteries and part of the circle of Willis. Brain aneurysms form here particularly often, and their rupture can cause subarachnoid haemorrhage.

Anterior ethmoidal artery

A branch of the ophthalmic artery that passes through the ethmoid bone into the anterior cranial fossa and nasal cavity. In sinus surgery it is an important landmark because of the risk of bleeding into the orbit.

Anterior inferior cerebellar artery

A branch of the basilar artery that supplies parts of the cerebellum and pons and often gives off the labyrinthine artery. Infarcts can cause dizziness, hearing loss and facial palsy.

Anterior ischaemic optic neuropathy

A circulatory disorder of the optic nerve head with sudden, painless loss of vision in one eye. The more common non-arteritic form is distinguished from the arteritic form in giant cell arteritis, which must be treated immediately with corticosteroids.

Anterior spinal artery

The artery running along the front of the spinal cord and supplying its front two thirds. Its occlusion causes anterior spinal artery syndrome with paralysis and loss of pain and temperature sensation below the lesion.

Anterior spinal artery syndrome

A spinal cord infarction in the territory of the anterior spinal artery. Paralysis and loss of pain and temperature sensation appear suddenly below the lesion, while position and touch sense remain intact.

Anterior tibial artery

The artery arising from the popliteal artery that supplies the extensor muscles of the lower leg. On the top of the foot it continues as the dorsalis pedis artery, whose pulse is checked in circulatory disorders.

Anthracyclines

A group of cytotoxic antibiotics such as doxorubicin, epirubicin, daunorubicin and idarubicin that insert between DNA strands and inhibit topoisomerase II. They work against many cancers but can permanently damage the heart muscle in a dose-dependent way.

Anti-amphiphysin antibodies

Onconeural antibodies found in paraneoplastic stiff person syndrome and neuropathies. Breast cancer or small cell lung cancer is often the cause.

Anti-beta-2 glycoprotein I antibodies

Antiphospholipid antibodies that, together with cardiolipin antibodies and lupus anticoagulant, are used to diagnose antiphospholipid syndrome. Detection must be confirmed after at least twelve weeks.

Anti-CASPR2 antibodies

Autoantibodies that can be associated with nerve hyperexcitability (neuromyotonia), pain, sleep disturbances and encephalitis. A thymoma is occasionally the cause.

Anti-CCP antibodies

Autoantibodies against cyclic citrullinated peptides that are highly specific for rheumatoid arthritis. They can be detectable years before the disease starts and suggest a more severe course.

Anti-DNase B titre

An antibody test against a streptococcal enzyme that indicates a past streptococcal infection. Especially after skin infections it is more informative than the antistreptolysin titre.

Anti-dsDNA antibodies

Autoantibodies against double-stranded DNA that are highly specific for systemic lupus erythematosus. Their level often rises during flares, especially with kidney involvement.

See also: Antinuclear antibodies (ANA)

Anti-GAD antibodies

Autoantibodies against the enzyme glutamate decarboxylase. They point to type 1 diabetes or LADA and, at very high levels, to rare neurological diseases such as stiff person syndrome.

Anti-ganglioside antibodies

Autoantibodies against glycolipids of the nerve membrane, such as GM1 or GD1a. They occur in variants of Guillain-Barré syndrome and in multifocal motor neuropathy.

Anti-GBM antibodies

Autoantibodies against the basement membrane of the glomeruli and alveoli. They cause Goodpasture syndrome with rapidly progressive nephritis and lung bleeding, an emergency.

Anti-GBM disease

A rare autoimmune disease with antibodies against the basement membrane of the kidneys and lungs that can rapidly cause kidney failure and lung bleeding.

Anti-GQ1b antibodies

Ganglioside antibodies detectable in most people with Miller Fisher syndrome. They explain the typical eye muscle paralysis and unsteady gait.

Anti-histone antibodies

Autoantibodies against histones, typical of drug-induced lupus, for example after hydralazine or procainamide. They also occur in ordinary lupus.

Anti-HMGCR antibodies

Autoantibodies against the enzyme HMG-CoA reductase, found in necrotising myopathy, sometimes after statin use. Unlike harmless statin muscle aches, this disease usually does not improve on stopping the statin alone.

Anti-Hu antibodies

An onconeural autoantibody usually associated with small cell lung cancer. It can cause nerve damage, encephalitis or cerebellar disorders, often before the tumour is found.

Anti-IA2 antibodies

Autoantibodies against the tyrosine phosphatase IA-2 in the pancreatic islet cells. Together with other islet autoantibodies they support the diagnosis of type 1 diabetes.

Anti-Jo-1 antibodies

Autoantibodies against a protein synthesis enzyme (histidyl-tRNA synthetase). They are the hallmark of antisynthetase syndrome with muscle inflammation, lung involvement and joint complaints.

Anti-La (SSB) antibodies

Autoantibodies (also called SS-B) found mainly in Sjögren’s syndrome and lupus, usually together with anti-Ro. In pregnancy they can contribute to congenital heart block in the baby.

Anti-LGI1 antibodies

Autoantibodies in a form of autoimmune encephalitis with memory problems, low sodium and brief, characteristic jerks of the arm and face. Early immunotherapy improves the outlook.

Anti-LKM-1 antibodies

Autoantibodies against a liver enzyme (cytochrome P450 2D6) that mark the rarer type 2 autoimmune hepatitis. It mainly affects children and young women.

Anti-LRP4 antibodies

Autoantibodies found in a small proportion of myasthenia gravis patients without acetylcholine receptor or MuSK antibodies. They disrupt signal transmission at the neuromuscular junction.

Anti-Ma2 antibodies

Onconeural antibodies in paraneoplastic inflammation of the limbic system, diencephalon or brainstem. In young men they are often associated with testicular tumours.

Anti-MAG antibodies

Antibodies against myelin-associated glycoprotein, usually occurring with an IgM gammopathy and causing a slowly progressive, mainly sensory polyneuropathy.

Anti-MCV antibodies

Antibodies against mutated citrullinated vimentin that, like anti-CCP antibodies, can indicate rheumatoid arthritis. They are used as a supplementary test in rheumatology.

Anti-MDA5 antibodies

Autoantibodies in a form of dermatomyositis with little muscle involvement but skin ulcers and a risk of rapidly progressive interstitial lung disease. Their detection requires close lung monitoring.

Anti-Mi-2 antibodies

Myositis-specific autoantibodies typical of classic dermatomyositis with pronounced skin signs. They are usually associated with a good response to treatment.

Anti-MPO antibodies

Antibodies against myeloperoxidase, usually corresponding to the pANCA pattern. They are found mainly in microscopic polyangiitis and eosinophilic granulomatosis with polyangiitis.

Anti-Müllerian hormone (AMH)

A hormone that roughly reflects the ovarian egg reserve, but it predicts natural fertility only to a limited extent.

Anti-MuSK antibodies

Autoantibodies against muscle-specific kinase at the neuromuscular junction. They are found in some myasthenia gravis patients without acetylcholine receptor antibodies.

Anti-NMDA receptor encephalitis

The most common antibody-mediated encephalitis, often affecting young women, with psychiatric symptoms, movement disorders, seizures and autonomic instability. An ovarian teratoma is sometimes the underlying cause.

Anti-PLA2R antibodies

Autoantibodies against the phospholipase A2 receptor on the glomeruli. They are typical of primary membranous nephropathy and are useful for monitoring its course.

Anti-PR3 antibodies

Antibodies against the enzyme proteinase 3 in neutrophils. They are the specific test result behind the cANCA pattern and typical of granulomatosis with polyangiitis.

Anti-Ri antibodies

Onconeural antibodies that can be associated with eye movement disorders (opsoclonus), unsteadiness and brainstem involvement. Breast or lung cancer is often the cause.

Anti-RNA polymerase III antibodies

Autoantibodies in systemic sclerosis associated with rapidly extensive skin thickening, renal crisis and a slightly increased cancer risk. Blood pressure and kidney values are therefore closely monitored.

Anti-Scl-70 antibodies

Autoantibodies against the enzyme topoisomerase I. They suggest diffuse systemic sclerosis and are associated with a higher risk of lung fibrosis.

See also: Antinuclear antibodies (ANA)

Anti-SLA antibodies

Autoantibodies against soluble liver antigen that are highly specific for autoimmune hepatitis and suggest a more severe course.

Anti-Sm antibodies

Autoantibodies against the Smith antigen in nuclear proteins. They occur in only some lupus patients but are then highly specific for systemic lupus erythematosus.

See also: Antinuclear antibodies (ANA)

Anti-smooth muscle antibodies

Autoantibodies against components of smooth muscle cells, especially actin. They are typical of type 1 autoimmune hepatitis but also occur at low levels in viral infections.

Anti-SRP antibodies

Autoantibodies against the signal recognition particle, found in immune-mediated necrotising myopathy, which causes marked muscle weakness and greatly raised creatine kinase.

Anti-SSA (Ro) antibodies

Autoantibodies against the Ro antigen, typical of Sjögren’s syndrome and lupus. In pregnancy they can cross to the baby and rarely cause congenital heart block.

Anti-THSD7A antibodies

A rare autoantibody in membranous nephropathy without anti-PLA2R. Its detection should prompt consideration of an underlying cancer.

Anti-U1-RNP antibodies

Autoantibodies that at high levels are characteristic of mixed connective tissue disease but also occur in lupus. They are among the extractable nuclear antigens.

Anti-VGCC antibodies

Autoantibodies against voltage-gated calcium channels at nerve endings, typical of Lambert-Eaton syndrome. When they are found, a targeted search for small cell lung cancer is carried out.

Anti-Xa activity

A laboratory test that measures the effect of heparins and factor Xa inhibitors in the blood. It helps with dosing, for example in kidney impairment or severe obesity.

Anti-Yo antibodies

An onconeural autoantibody against Purkinje cells of the cerebellum. It occurs mainly with ovarian and breast cancer and causes rapidly progressive unsteadiness.

Antiarrhythmic drugs

Medicines for heart rhythm disorders, classified by their site of action, such as sodium channel blockers, beta blockers, potassium channel blockers and calcium channel blockers. Many can themselves trigger arrhythmias, so ECG monitoring is important.

Antibiogram

A laboratory test showing which antibiotics a cultured pathogen is sensitive or resistant to. It allows targeted rather than broad treatment.

Antibiotic

A medicine that kills bacteria or stops them growing. Antibiotics do not work against viruses, and unnecessary use promotes resistance.

Antibiotic stewardship

Programmes in hospitals and practices that promote targeted, correctly dosed and as short as possible antibiotic use. The aim is to secure treatment success and slow the development of resistance.

Antibody

Y-shaped proteins (immunoglobulins) produced by the immune system to recognise and tag pathogens and foreign substances. Laboratory-made (monoclonal) antibodies are also used as medicines.

Antibody avidity

A measure of how firmly IgG antibodies bind to their antigen; binding strengthens over the course of an infection. A low avidity index therefore suggests a recently acquired infection, which matters in pregnancy for toxoplasmosis or CMV, for example.

Antibody-drug conjugate

An antibody linked to a cell toxin so that the toxin is delivered specifically to cancer cells.

Antibody screening test

A blood test before transfusions and in pregnancy that looks for irregular antibodies against foreign blood group antigens. A positive result requires identifying the antibody and selecting compatible blood.

Antibody titre

A measure of the amount of a specific antibody in the blood, often given as the highest dilution at which it is still detectable. It is measured, for example, to check vaccine protection or to detect an infection.

Anticentromere antibodies

Autoantibodies against proteins of the chromosome constriction, showing a typical speckled pattern on immunofluorescence. They are characteristic of limited systemic sclerosis.

See also: Antinuclear antibodies (ANA)

Anticholinergic syndrome

Poisoning caused by substances that inhibit acetylcholine, with flushed, dry skin, dilated pupils, racing heart, fever and confusion. In certain cases physostigmine is an antidote.

Anticholinergics

Drugs that block the messenger acetylcholine, used for example for overactive bladder or airway narrowing. Typical side effects are dry mouth, constipation and, in older people, confusion.

Anticipation (genetics)

In genetics, the earlier onset or more severe course of an inherited disease from generation to generation. It is typical of trinucleotide repeat disorders such as myotonic dystrophy or Huntington’s disease, because the repeats lengthen when passed on.

Anticoagulation

Inhibiting blood clotting with medicines (“blood thinners”) to prevent thrombosis, embolism and stroke, for example in atrial fibrillation.

Antidepressant

A medicine for treating depression, often also used for anxiety and obsessive-compulsive disorders. The effect usually starts only after two to four weeks.

Antidiarrhoeals

Medicines against diarrhoea, such as loperamide, which slows bowel movement. With fever or bloody stools they should not be taken without medical advice.

Antidote

A remedy that specifically reverses or weakens the effect of a poison or drug. Examples are naloxone for opioids, acetylcysteine for paracetamol and flumazenil for benzodiazepines.

Antiemetic

A medicine against nausea and vomiting that acts on various receptors in the vomiting centre or the gut. Depending on the cause, serotonin antagonists, dopamine antagonists or antihistamines may be used.

Antiepileptic drugs

Medicines that prevent epileptic seizures by damping the excitability of nerve cells.

Antifungal

A medicine against fungal infections, for example as a cream, nail lacquer or tablet.

Antigen

A structure, such as a protein on a pathogen, that the immune system recognises and that triggers a defence response.

Antigen presentation

The process by which cells display protein fragments on their surface via HLA molecules so that T cells can recognise them. Dendritic cells are the most important initiators of a specific immune response.

Antihistamine

A medicine that blocks the messenger substance histamine and relieves allergic symptoms such as sneezing, itching and hives.

Antihypertensives

Blood-pressure-lowering medicines, such as ACE inhibitors, sartans, calcium channel blockers and diuretics.

Antimitochondrial antibodies

Autoantibodies against components of mitochondria, detectable in more than 90 per cent of people with primary biliary cholangitis. They can precede the disease by years.

Antinuclear antibodies (ANA)

Autoantibodies against components of the cell nucleus; a pointer to autoimmune diseases such as lupus, though they also occur in healthy people.

Antioxidants

Substances such as vitamin C, vitamin E or polyphenols that neutralise free radicals. High-dose supplements have mostly shown no benefit in studies.

Antiparasitic drugs

Medicines against parasites such as worms, lice, mites or malaria parasites. Very different agents are used depending on the organism, for example mebendazole, permethrin or ivermectin.

Antiphospholipid antibodies

Autoantibodies against phospholipid-binding proteins, including lupus anticoagulant, anticardiolipin and anti-beta-2 glycoprotein antibodies. Repeated detection together with thromboses or pregnancy complications establishes antiphospholipid syndrome.

Antiphospholipid syndrome

An autoimmune disease in which antibodies against phospholipid-binding proteins promote clotting. Consequences are thromboses in veins or arteries and recurrent miscarriages; it is treated with anticoagulants.

Antisense oligonucleotide

A short synthetic nucleic acid strand that binds specifically to a particular messenger RNA and so inhibits its translation or alters splicing. Drugs such as nusinersen for spinal muscular atrophy work on this principle.

Antiseptic

An agent that kills or inhibits pathogens on the skin, mucous membranes or in wounds, for example octenidine or povidone-iodine.

Antisocial personality disorder

A personality disorder with repeated disregard for social norms and the rights of others, impulsivity and lack of guilt. The patterns usually begin in adolescence.

Antistreptolysin O titre

A blood test measuring antibodies against a toxin of group A streptococci, indicating a past infection because it rises only one to three weeks afterwards. It is used when complications such as rheumatic fever or glomerulonephritis are suspected, not to diagnose acute tonsillitis.

Antisynthetase syndrome

A rare autoimmune disease with antibodies against aminoacyl-tRNA synthetases, such as anti-Jo-1. Typical is the combination of muscle inflammation, interstitial lung disease, joint complaints, Raynaud’s phenomenon and cracked skin on the fingers (mechanic’s hands).

Antithrombin

A natural protein that inhibits activated clotting factors and so prevents excessive clotting. An inherited deficiency raises the risk of thrombosis.

Antithrombin deficiency

A congenital or acquired deficiency of antithrombin, a natural anticoagulant. It markedly increases the risk of venous thrombosis and can weaken the effect of heparin.

Antithymocyte globulin

Animal-derived antibodies against human T cells used to prevent or treat transplant rejection and in aplastic anaemia. Infusion reactions and infections are important risks.

Antley-Bixler syndrome

A very rare malformation with premature fusion of the skull sutures, midface hypoplasia, fused elbow bones and sometimes disturbed steroid hormone production (POR deficiency).

Anton syndrome

Cortical blindness after damage to the visual cortex on both sides, in which affected people are unaware of their blindness and describe visual impressions that do not exist.

Anuria

Almost complete absence of urine output, less than about 100 millilitres per day. It is a warning sign of kidney failure or complete urinary obstruction.

Anxiety disorder

Mental illness with excessive, persistent anxiety that impairs daily life, such as panic disorder, phobias or generalised anxiety disorder. Psychotherapy is very effective.

In depth: Anxiety Disorders →

AO classification

An alphanumeric system of the AO Foundation for uniformly describing bone fractures by bone, region and fracture pattern. It facilitates treatment planning and scientific comparisons.

AOFAS score

A clinical score of the American Orthopaedic Foot and Ankle Society for assessing pain, function and alignment of the ankle, hindfoot, midfoot and forefoot.

Aorta

The main artery and largest blood vessel in the body. It carries oxygen-rich blood from the left ventricle into the systemic circulation.

Aortic aneurysm

An abnormal widening of the main artery in the chest or abdomen that often causes no symptoms for a long time. Above a certain size or with rapid growth, surgery or a stent graft is used because of the risk of rupture.

Aortic arch

The curved section of the main artery just above the heart, from which the large arteries to the head and arms arise. Its wall contains pressure sensors involved in blood pressure regulation.

Aortic dissection

A life-threatening tear in the inner layer of the main artery with sudden, tearing chest or back pain – an emergency.

Aortic regurgitation

A leaking aortic valve that lets blood flow back into the left ventricle during relaxation. Over time the ventricle can enlarge and weaken.

Aortic stenosis

Narrowing of the aortic valve, often age-related; it can cause breathlessness, chest pain and fainting.

APACHE II score

An intensive care score that estimates illness severity and probability of death from vital signs, laboratory values, age and pre-existing conditions in the first 24 hours. It serves mainly quality assurance and research rather than individual decisions.

Apalutamide

An androgen receptor inhibitor for prostate cancer, combined with androgen deprivation. Side effects include rash, fatigue, falls and an underactive thyroid.

Apathy

Lack of interest, drive and emotional expression, for example in dementia, depression or after brain injury.

APECED

Autoimmune polyendocrine syndrome type 1, caused by mutations in the AIRE gene, which controls self-tolerance in the thymus. Typical are chronic Candida infections of the skin and mucous membranes, underactive parathyroid glands and adrenal insufficiency.

Apert syndrome

An inherited malformation in which the skull sutures fuse too early and fingers and toes are fused. It is caused by a mutation in the FGFR2 gene, and several operations in childhood are usually needed.

Apexification

Treatment of a tooth with a dead pulp and a still-open root tip, creating a tight seal at the root end. It is used mainly in young patients after dental trauma.

Apfel score

A simple score estimating the risk of postoperative nausea and vomiting from four factors: female sex, non-smoking status, previous nausea after anaesthesia or motion sickness, and opioids after surgery. Each factor adds about 20 percentage points.

Apgar score

A scoring system for assessing newborns one, five and ten minutes after birth based on breathing, pulse, muscle tone, skin colour and reflexes. It gives a quick assessment of adaptation after birth.

Aphakia

Absence of the lens of the eye, for example after surgery without a lens implant, injury or congenitally. The eye is then highly long-sighted and needs an artificial lens, contact lens or aphakic glasses.

Aphasia

A language disorder after brain damage, for example from a stroke.

Apheresis

A procedure in which blood is separated into its components outside the body and only one part is removed or collected, for example for plasma donation or removal of harmful antibodies.

Aphonia

Complete loss of voice, so that only whispering is possible. Causes include laryngitis, vocal cord paralysis or psychological stress.

Apical periodontitis

Inflammation of the tissue around the root tip, usually as a result of a dead or infected dental pulp. It appears as a dark area on X-ray and is usually treated with root canal treatment.

Apixaban

A direct oral anticoagulant (factor Xa inhibitor) for preventing stroke in atrial fibrillation and for treating thrombosis.

Aplasia

Failure of an organ or tissue to develop despite a primordium being present; more broadly also the cessation of cell production, for example in the bone marrow in aplastic anaemia. The term is often used loosely alongside agenesis.

Aplastic anaemia

A rare disease in which the bone marrow produces hardly any blood cells, so all cell lines are reduced. The cause is usually an autoimmune reaction.

Apley test

A meniscus test performed lying face down: with the knee bent, the lower leg is rotated under pressure; pain suggests meniscus damage, while pain under traction points rather to a ligament injury.

Apnoea

A pause in or cessation of breathing. In sleep apnoea, breathing repeatedly stops during sleep.

Apnoea test

A test in brain death diagnosis in which ventilation is paused while oxygen is given, to check whether spontaneous breathing starts despite markedly rising carbon dioxide. Its absence indicates loss of the brainstem respiratory centre.

Apnoeic oxygenation

Giving oxygen through the nose while the patient is not breathing, for example during intubation. Oxygen flows passively into the lungs and delays a fall in saturation.

Apocrine sweat glands

Scent glands in the armpits and genital and anal regions that release a protein- and fat-rich secretion into the hair follicles from puberty. Typical body odour arises only through bacterial breakdown.

Apolipoprotein A1

The main protein of HDL cholesterol, involved in transporting cholesterol back to the liver. The ratio of apolipoprotein B to A1 is used as an additional cardiovascular risk marker.

Apolipoprotein B

A structural protein found exactly once on every atherogenic lipoprotein particle such as LDL. Its blood level therefore reflects the number of vessel-damaging particles and can sometimes describe cardiovascular risk better than LDL cholesterol.

Apomorphine

A dopamine agonist used in Parkinson’s disease as a pen injection to quickly bridge off periods or as a continuous infusion. Despite its name it is not an opioid; nausea is a common side effect.

Aponeurosis

A flat, tendinous sheet through which muscles attach or transmit force, for example in the abdominal wall or palm. Thickening of the palmar aponeurosis leads to Dupuytren’s contracture.

Apoptosis

Programmed cell death: an orderly self-destruction process by which the body removes damaged or surplus cells without triggering inflammation.

Apparent mineralocorticoid excess

A rare disorder in which the enzyme 11-beta-HSD2 does not adequately inactivate cortisol in the kidney, so cortisol acts like aldosterone. Consequences are high blood pressure and low potassium; heavy liquorice consumption can have a similar effect.

Appendicectomy

Surgical removal of the appendix, usually for appendicitis and nowadays mostly by keyhole surgery. It is one of the most common emergency operations.

Appendicitis

Inflammation of the vermiform appendix. Typical signs are pain moving from the navel to the lower right abdomen, nausea and fever; surgery is usually performed.

Appendicular artery

An end artery from the ileocolic artery running in the mesoappendix to the appendix. It is tied off during appendicectomy; because it has no collaterals, its thrombosis promotes perforation.

Apple core sign

A short, ring-shaped narrowing of the bowel with overhanging edges on contrast X-ray that looks like a bitten apple. It is suspicious for bowel cancer.

Apprehension test

A shoulder stability test in which the arm is abducted and externally rotated. The patient’s apprehension or guarding suggests anterior shoulder instability after dislocation.

Approximal plaque index

An index giving the percentage of interdental spaces covered with plaque. It is used to monitor and motivate oral hygiene.

Apraxia

Inability to carry out learned purposeful movements even though strength, sensation and understanding are preserved. It occurs, for example, after left-hemisphere strokes or in dementia.

Apremilast

A tablet that inhibits the enzyme phosphodiesterase-4 in immune cells and lowers inflammatory messengers. It is used for psoriasis, psoriatic arthritis and Behçet’s disease.

Aprepitant

An antiemetic that blocks neurokinin-1 receptors in the brain and mainly prevents delayed nausea after highly emetogenic chemotherapy. It is usually combined with a setron and dexamethasone.

Aprocitentan

A dual endothelin receptor antagonist for add-on treatment of resistant hypertension. Fluid retention is common; because it can harm the foetus, it must not be used in pregnancy.

Aprotinin

An inhibitor of protein-splitting enzymes that slows clot breakdown and reduces blood loss in heart surgery. In the EU it is now authorised only to a limited extent for certain bypass operations.

Aqua jogging

Running movements in deep water, usually with a buoyancy belt and without touching the bottom. Buoyancy relieves the joints, so aqua jogging is often used in rehabilitation and for people with obesity.

Aquagenic pruritus

Intense itching immediately after contact with water without visible skin changes. It can be an early sign of polycythaemia vera, so a blood count is advisable.

Aquagenic urticaria

A very rare form of hives in which skin contact with water of any temperature triggers small itchy wheals within minutes.

Aquaporin-4 antibodies

Autoantibodies against the water channel aquaporin-4 on astrocytes, highly specific for neuromyelitis optica spectrum disorder. Detecting them distinguishes this disease from multiple sclerosis, which is important for choosing treatment.

Aquaporins

Protein channels in cell membranes through which water can pass rapidly. In the kidney, ADH inserts aquaporin-2 into the collecting ducts to conserve water; aquaporin-4 in the brain is the target of autoantibodies in neuromyelitis optica.

Aqueduct of Sylvius

A narrow channel in the midbrain connecting the third and fourth ventricles. Narrowing causes a build-up of cerebrospinal fluid and thus hydrocephalus.

Arachnodactyly

Strikingly long, slender fingers and toes, also called “spider fingers”. It is a typical feature of Marfan syndrome and can point to other connective tissue disorders.

Arachnoid cyst

A usually congenital cavity filled with cerebrospinal fluid between the layers of the arachnoid. It is often found by chance and usually harmless; surgery is needed only if it causes pressure symptoms.

Arachnoid granulations

Protrusions of the arachnoid into the venous sinuses of the brain through which cerebrospinal fluid drains back into the blood. Larger forms are called Pacchionian granulations.

Arachnoid mater

The delicate middle layer of the meninges, lying like a spider’s web between the tough outer and the soft inner layer. Cerebrospinal fluid circulates beneath it; bleeding into this space is called subarachnoid haemorrhage.

ARCO classification

A staging system of the Association Research Circulation Osseous for osteonecrosis of the femoral head based on X-ray and MRI, from early changes to osteoarthritis. It helps choose between joint-preserving treatment and joint replacement.

Arcuate artery of the foot

An arched artery on the top of the foot from the dorsalis pedis artery, giving rise to the arteries on the backs of the toes. In many people it is only weakly developed.

Arcus senilis

A grey-white ring at the edge of the cornea caused by fat deposits. In older age it is usually harmless; in younger people it may point to raised blood lipids.

ARDS

Acute respiratory distress syndrome: acute lung failure due to severe inflammation, for example in pneumonia or sepsis.

Area postrema

A small region on the floor of the fourth ventricle without a complete blood-brain barrier that detects toxins in the blood. It triggers nausea and vomiting and is the target of many antiemetics.

Areflexia

Absence of tendon reflexes on neurological examination. It occurs, for example, in polyneuropathies, Guillain-Barré syndrome or nerve root damage.

Argatroban

A direct thrombin inhibitor given by infusion that works independently of antithrombin. It is used mainly in heparin-induced thrombocytopenia type II as a substitute for heparin.

Arginase deficiency

A very rare inherited urea cycle disorder in which arginine rises in the blood. A slowly progressive spastic paralysis of the legs in childhood is typical; treatment is with a low-protein diet and, where appropriate, an arginine-degrading enzyme preparation.

Argininosuccinic aciduria

An inherited urea cycle disorder in which ammonia is not adequately detoxified. Besides metabolic crises with hyperammonaemia, brittle hair (trichorrhexis nodosa) and liver involvement are typical.

Argyll Robertson pupil

Small, often irregular pupils that barely react to light but respond normally to near focusing. It is a classic sign of neurosyphilis.

Arimoclomol

A drug for Niemann-Pick disease type C intended to support the cellular stress response and lysosomal function. It is usually given with miglustat and can slow progression but does not cure the disease.

Aripiprazole

An antipsychotic that acts as a partial agonist at dopamine receptors and is used for schizophrenia and mania. It causes relatively little weight gain but can trigger inner restlessness.

Arm sling

A triangular bandage or sling that holds the forearm bent in front of the body and relieves the shoulder, arm or hand, for example after injuries or surgery.

Arnica

A medicinal plant whose preparations are traditionally applied externally for bruises, sprains and contusions. It must not be used on open wounds and can cause allergies.

Aromatase inhibitors

Medicines that reduce oestrogen production after the menopause; used for hormone-sensitive breast cancer.

Aromatherapy

The use of essential oils for inhalation or massage to promote well-being. Benefit beyond relaxation is hardly proven; the oils can irritate the skin and airways and can be dangerous for young children.

Arpraziquantel

A child-friendly dispersible tablet containing the active enantiomer of praziquantel for treating schistosomiasis in young children. It fills a treatment gap for children under six in affected regions.

Array CGH

A genetic test that checks the entire genome for missing or extra segments too small to see under a light microscope. It is used, for example, in developmental delay or malformations.

Arrhythmia

Heart rhythm disorder in which the heart beats too fast, too slowly or irregularly. Many forms are harmless, but some can be dangerous.

Arrhythmogenic right ventricular cardiomyopathy

An inherited heart muscle disease in which muscle, mainly of the right ventricle, is replaced by fat and fibrous tissue. It can trigger dangerous arrhythmias in young athletes.

Arsenic poisoning

Poisoning by arsenic compounds: acutely with vomiting and diarrhoea, chronically, for example from contaminated well water, with skin discolouration, thickened skin, nerve damage and increased cancer risk.

Arsenic trioxide

An arsenic compound that, together with all-trans retinoic acid, can cure acute promyelocytic leukaemia in most cases by making the leukaemia cells mature. Risks include QT prolongation on the ECG and differentiation syndrome.

Artemether-lumefantrine

A fixed combination for treating uncomplicated falciparum malaria. Artemether rapidly reduces parasite numbers and lumefantrine clears the remaining parasites; taking it with fatty food improves absorption.

Arterial line

A cannula placed in an artery, usually at the wrist, for continuous blood pressure monitoring and repeated blood gas analyses. It is used in major surgery and intensive care.

Arterial switch operation

A corrective operation for transposition of the great arteries in which the aorta and pulmonary artery, together with the coronary arteries, are moved to the correct ventricle. It is usually done in the first weeks of life.

Arteriole

The smallest artery before the capillary network, with a strong muscular wall. By narrowing and widening, arterioles regulate vascular resistance and thus largely determine blood pressure.

Arteriovenous malformation

A congenital vascular malformation in which arteries connect directly to veins without a capillary network. In the brain it can cause bleeding or epileptic seizures.

Artery

A blood vessel that carries blood away from the heart. In the systemic circulation, arteries carry oxygen-rich blood.

Artery of Adamkiewicz

The largest feeding artery of the lower spinal cord, usually from a left intercostal or lumbar artery between the 9th and 12th thoracic vertebrae. Injury or occlusion during aortic surgery can cause paraplegia.

Artesunate

A water-soluble artemisinin derivative that, given by infusion, is the treatment of choice for severe falciparum malaria and kills blood parasites very quickly. Delayed haemolysis can occur after treatment, so blood counts are checked.

Arthralgia

Joint pain without necessarily visible inflammation, for example in viral infections or osteoarthritis.

Arthritis

Joint inflammation with swelling, pain and warmth, for example in rheumatic disease, gout or infections.

Arthrodesis

Surgical stiffening of a joint to relieve pain when it is severely destroyed. Typical sites are the ankle and the big toe joint.

Arthrogryposis multiplex congenita

An umbrella term for congenital joint stiffness in several body regions, usually caused by lack of movement of the unborn baby in the womb. Early physiotherapy, splints and surgery improve mobility.

Arthroscopy

Keyhole examination and treatment of a joint through small incisions using a camera and instruments, often on the knee.

Articaine

The most widely used amide-type local anaesthetic in dentistry; it penetrates bone well and is broken down quickly in the blood. It is usually combined with adrenaline to last longer.

Artichoke

A vegetable whose leaf extract is traditionally used for fullness, bloating and mild digestive complaints. It stimulates bile flow.

Artificial disc replacement

Artificial replacement of a disc in the cervical or lumbar spine intended to preserve the segment’s mobility. It is only suitable for selected patients without marked facet joint arthritis.

ASA classification

A classification of physical status before anaesthesia into six classes, from a healthy patient to a brain-dead organ donor. It is used for risk assessment before procedures.

Asbestosis

Lung fibrosis caused by years of inhaling asbestos fibres, appearing only decades after exposure. Asbestos also raises the risk of lung cancer and mesothelioma.

ASCA

Antibodies against baker’s yeast, Saccharomyces cerevisiae. They are found more often in Crohn’s disease than in ulcerative colitis and can help distinguish the two, but are not conclusive on their own.

Ascariasis

Infection with the roundworm, usually via contaminated food or soil. It often goes unnoticed, but heavy infestation can cause abdominal pain and bowel obstruction.

Ascaris lumbricoides

The large roundworm, a nematode up to 40 cm long whose eggs are ingested with contaminated food. The larvae migrate through the lungs before settling in the small intestine.

Ascending pharyngeal artery

A thin branch of the external carotid artery running to the pharynx, middle ear and dura. It is important for embolisation treatment of skull base tumours.

Asciminib

A drug for chronic myeloid leukaemia that binds to a different site on the BCR-ABL protein than classic tyrosine kinase inhibitors, so it can work even when there is resistance to them.

Ascites

Accumulation of fluid in the abdominal cavity, often due to liver cirrhosis.

ASDAS

A composite activity score for axial spondyloarthritis that combines patient-reported items with CRP or ESR. It distinguishes inactive, low, high and very high disease activity.

Asenapine

An atypical antipsychotic placed under the tongue as a dissolving tablet and used for manic episodes in bipolar disorder. Temporary numbness of the mouth and drowsiness are common side effects.

Asepsis

All measures that prevent germs from being introduced during procedures, such as sterile technique and sterile instruments. It differs from antisepsis, which kills germs already present.

Aseptic technique

A way of working in which sterile materials and handling prevent germs from entering wounds, catheters or body cavities. It is the basis of dressing changes and invasive procedures.

Asfotase alfa

Enzyme replacement therapy for hypophosphatasia that replaces the missing tissue-nonspecific alkaline phosphatase. It improves bone mineralisation, especially in early-onset forms.

Asherman syndrome

Scar tissue inside the uterine cavity, usually after curettage. It can lead to scanty or absent periods and infertility.

Ashworth scale

A clinical scale for assessing spasticity that rates resistance to passive movement of a joint from 0 (normal) to 4 (rigid). The modified version with an intermediate grade 1+ is usually used.

ASIA Impairment Scale

A standardised classification of spinal cord injuries into grades A to E according to the international ISNCSCI examination rules, based on strength, sensation and preserved function in the lowest sacral segment.

Asomatognosia

A disorder in which one half of the body is not recognised as one’s own, usually after a right-sided stroke. Affected people may think their arm belongs to someone else.

Asparaginase

An enzyme that breaks down the amino acid asparagine in the blood; acute lymphoblastic leukaemia cells cannot make enough of it themselves and die. It is obtained from bacteria such as E. coli or Erwinia and can cause allergies, pancreatitis and clotting disorders.

Aspartylglucosaminuria

A rare lysosomal storage disease caused by deficiency of the enzyme aspartylglucosaminidase. Children develop progressive intellectual disability, coarse facial features and behavioural problems.

ASPECTS

A ten-point score for assessing early signs of infarction in the territory of the middle cerebral artery on CT. Each affected area subtracts one point; low values indicate an extensive infarct and influence treatment decisions.

Asperger syndrome

Formerly a separate diagnosis for a form of autism without language delay or intellectual disability, with difficulties in social interaction and intense special interests. In ICD-11 it is part of autism spectrum disorder.

Aspergilloma

A spherical fungal ball of Aspergillus that settles in a pre-existing lung cavity, for example after tuberculosis. It often causes few symptoms but can lead to coughing up blood; heavy bleeding requires surgery.

Aspergillosis

Infection with moulds of the genus Aspergillus, dangerous mainly in people with weakened immunity.

Aspergillus fumigatus

A mould found worldwide whose spores are inhaled constantly. In people with weakened immunity or pre-existing lung damage it can cause aspergillosis.

Aspiration

Entry of saliva, food or stomach contents into the airways, often in people with swallowing difficulties. It can lead to aspiration pneumonia; adapted diets and sitting upright to eat help prevent it.

Aspiration pneumonia

Pneumonia that develops when stomach contents, saliva or food enter the airways. People with swallowing disorders, impaired consciousness or after anaesthesia are particularly at risk.

Aspiration prevention

Measures to prevent saliva, food or fluid entering the airways, especially in people with swallowing difficulties. They include sitting upright to eat, adapted diets, swallowing training and good oral care.

Asplenia

Absence or loss of function of the spleen, congenital, after surgery or, for example, in sickle cell disease. Affected people are especially at risk from infections with encapsulated bacteria such as pneumococci and need specific vaccinations.

ASRS

A WHO self-report questionnaire for recording ADHD symptoms in adults; the short six-question version is used for screening.

Assisted living

A form of housing for older people with their own apartment and additional basic services such as an emergency call system and contact persons. Care is not automatically included but can be added.

Astereognosis

Inability to recognise objects by touch alone although touch and movement are preserved. It points to a disorder in the opposite parietal lobe.

Asterixis

A coarse, flapping drop of the outstretched hands caused by brief lapses in muscle tone. It typically occurs in liver failure, kidney failure or carbon dioxide retention.

Asteroid hyalosis

Harmless deposits of many small white calcium-lipid bodies in the vitreous, usually in one eye in older people. It rarely affects vision but makes examining the back of the eye more difficult.

Asthenopia (eye strain)

Complaints from overworked eyes such as burning, headache and blurred vision, for example after long screen work or with uncorrected refractive errors. Breaks and suitable glasses help.

Asthma control test

A short questionnaire with five questions on symptoms, night waking, reliever use and limitations over the past four weeks. The score shows whether asthma is well controlled, partly controlled or uncontrolled.

Astigmatism

An unevenly curved cornea that causes distorted vision.

Astrocyte

A star-shaped glial cell of the central nervous system. Astrocytes support nerve cells, regulate ion and neurotransmitter balance, contribute to the blood-brain barrier and form glial scars after injury.

Astrocytoma

A brain tumour arising from the star-shaped supporting cells of the brain. Depending on grade, it ranges from slow-growing tumours in children to glioblastoma.

Astrovirus

An RNA virus that mainly causes mild diarrhoeal illness in young children. Rare severe courses with encephalitis have been described in immunocompromised people.

Asundexian

An oral factor XIa inhibitor intended to prevent thrombosis without greatly impairing haemostasis. In atrial fibrillation it was inferior to apixaban in a large trial; it is being studied mainly for secondary stroke prevention.

Asymmetric tonic neck reflex

An infant reflex: when the head of a baby lying down is turned to one side, the arm and leg on the face side extend and the limbs on the back-of-head side bend (“fencing posture”). Persistence beyond the first months of life may indicate a brain disorder.

Asymptomatic bacteriuria

Bacteria in the urine without symptoms of a urinary tract infection. It is usually not treated, except for example before urological procedures.

Asystole

Absence of any electrical heart activity on the ECG with cardiac arrest. Defibrillation does not help here; chest compressions, ventilation, adrenaline and the search for treatable causes are the priority.

Ataluren

A drug intended to allow reading through premature stop signals in genetic information and used in Duchenne muscular dystrophy with nonsense mutations. Because benefit could not be confirmed in studies, its conditional EU authorisation was not renewed.

Ataxia

Impaired coordination of movement with an unsteady gait and imprecise movements, often in diseases of the cerebellum.

Ataxia telangiectasia

A rare inherited disease (ATM gene) with progressive unsteadiness from early childhood, dilated small vessels in the eyes and skin, immune deficiency and a markedly increased cancer risk. X-rays should be used as sparingly as possible.

Atazanavir

An HIV protease inhibitor usually boosted with ritonavir or cobicistat. A harmless rise in indirect bilirubin with yellowing of the eyes is typical; acid-reducing drugs decrease its absorption.

Atelectasis

A collapsed, airless section of lung, for example after surgery.

Atenolol

A beta-1-selective beta blocker excreted largely unchanged by the kidneys. It lowers heart rate and blood pressure; the dose must be adjusted in impaired kidney function.

Atezolizumab

A checkpoint antibody against PD-L1 that releases a brake on the immune system. It is used, among others, in lung, liver and bladder cancer.

Atherosclerosis

Deposits of fat, calcium and connective tissue in artery walls (“hardening of the arteries”). It narrows the vessels and is the main cause of heart attack, stroke and poor circulation in the legs.

Athetosis

Slow, writhing, involuntary movements, especially of the fingers and hands. It results from damage to the basal ganglia, for example after early childhood brain injury.

Atidarsagene autotemcel

A gene therapy for metachromatic leukodystrophy: the patient’s own blood stem cells are given a working copy of the ARSA gene in the laboratory and returned. It is mainly an option in the early stage with few symptoms.

Atlanta classification

The internationally used definition of acute pancreatitis, revised in 2012, classifying mild, moderately severe and severe courses with uniform terms for fluid collections and necrosis.

Atlantoaxial instability

Excessive mobility between the first and second cervical vertebrae that can endanger the spinal cord. It occurs, among others, in rheumatoid arthritis, Down syndrome or after injuries; warning signs are neck pain, gait disturbance and tingling in the arms.

Atlas (first cervical vertebra)

The first neck vertebra, which carries the skull and is ring-shaped without a vertebral body. Together with the second cervical vertebra it allows nodding and turning of the head.

ATLS

Advanced Trauma Life Support: a widely used training concept for the structured initial care of severely injured patients using the ABCDE approach. Life-threatening problems are identified and treated in a fixed order.

Atogepant

A gepant tablet that blocks the CGRP receptor and is taken daily to prevent migraine. Constipation and nausea are common.

Atomoxetine

A non-stimulant ADHD medicine that inhibits noradrenaline reuptake. The full effect appears only after weeks; there is no relevant potential for misuse.

Atopy

An inherited tendency to over-react to harmless environmental substances with IgE antibodies. The atopic group of conditions includes atopic eczema, hay fever and allergic asthma.

Atorvastatin

A widely prescribed statin that lowers LDL cholesterol and helps prevent heart attacks and strokes.

Atosiban

A labour-inhibiting drug that blocks oxytocin receptors and is given by infusion in preterm labour to gain time for the baby’s lung maturation.

Atovaquone-proguanil

A combination of two antimalarials used both for prevention when travelling and for treating uncomplicated malaria. For prevention it is taken daily during the stay and for seven days afterwards.

ATP

Adenosine triphosphate, the universal energy currency of cells; splitting off a phosphate group releases energy for muscle work, transport and synthesis. It is produced mainly in the mitochondria.

Atracurium

A non-depolarising muscle relaxant for anaesthesia that breaks down spontaneously in the blood independently of the liver and kidneys (Hofmann elimination). It can release histamine, causing flushing and a drop in blood pressure.

Atrasentan

A selective endothelin A receptor antagonist that reduces protein excretion in the urine in IgA nephropathy. Because it can harm the foetus, reliable contraception is required during treatment.

Atraumatic restorative treatment

A minimally invasive caries treatment in which soft decayed tissue is removed with hand instruments only and the cavity is filled with glass ionomer cement. It is possible without a drill and often without anaesthesia.

ATRIA score

A score estimating bleeding risk under anticoagulation in atrial fibrillation from anaemia, severe kidney impairment, age 75 or over, previous bleeding and high blood pressure.

Atrial natriuretic peptide

A hormone from the atria of the heart released when they are stretched by increased blood volume. It promotes excretion of sodium and water and widens blood vessels.

Atrioventricular septal defect

A congenital heart defect with a hole in the centre of the heart’s septum and malformed valves between the atria and ventricles. It is more common in trisomy 21 and is usually operated on in the first year of life.

Atrophic gastritis

Chronic inflammation of the stomach lining with loss of glands, usually after long-standing Helicobacter infection or autoimmune. It can lead to vitamin B12 and iron deficiency and increases the risk of stomach cancer.

Atrophie blanche

Whitish, depressed, scar-like skin patches with red dots, usually at the ankle in chronic venous insufficiency. The areas heal poorly and tend to develop very painful ulcers.

Atrophy

Shrinking or wasting of a tissue or organ, for example muscle wasting from lack of movement.

Atropine

A drug that inhibits the parasympathetic nervous system, raising heart rate, dilating the pupils and reducing secretions. It is used for very slow heart rates and certain poisonings.

Attachment disorder

A childhood disorder in which children do not form secure relationships after severe neglect or frequent changes of caregivers. It shows as inhibited withdrawal or as indiscriminate approach to strangers.

Attachment loss

Loss of the connective tissue attachment of the tooth to root cementum and jawbone, measured in millimetres. It is the key measure of the severity of periodontitis.

Attributable risk

The proportion of disease risk attributable to a particular risk factor. It is calculated as the difference in risk between exposed and unexposed people.

Attrition (dental)

Loss of hard tooth tissue through direct tooth-to-tooth contact, for example during chewing or night-time grinding. The biting edges become flat and shiny.

Atypical fibroxanthoma

A rapidly growing skin tumour on the sun-damaged scalp of older people. It is usually benign in behaviour but must be completely removed and distinguished from pleomorphic sarcoma.

Atypical haemolytic uraemic syndrome

A rare form of HUS triggered not by EHEC bacteria but by uncontrolled activation of the complement system. It damages the kidneys and small vessels and is treated with complement inhibitors such as eculizumab.

Audiogram

A graph of the hearing threshold at different pitches, separately for air and bone conduction. It shows whether hearing loss affects the middle or the inner ear.

Audiology

The science of hearing and its disorders, including hearing tests, hearing aids and cochlear implants. It combines medicine, acoustics and technology.

Audiometry

Hearing test that measures hearing ability across different pitches and volumes.

AUDIT test

A ten-question WHO questionnaire on drinking amount, signs of dependence and alcohol-related problems. It often detects risky drinking earlier than laboratory values.

Auditory neuropathy

A hearing disorder in which the outer hair cells work but signal transmission to the auditory nerve is disturbed. Otoacoustic emissions are present, while brainstem audiometry is abnormal.

Auditory processing disorder

A disorder in which hearing works normally but the brain processes sounds poorly. Affected children have difficulty understanding speech in noisy surroundings, for example.

Auer rods

Rod-shaped inclusions in immature blood cells that suggest acute myeloid leukaemia. They consist of fused granules.

See also: Acute myeloid leukaemia

Aura

Temporary visual or sensory disturbances, such as flickering or zigzag lines, that can precede a migraine attack.

Auramine staining

A fluorescent stain for acid-fast bacilli used to search quickly for tuberculosis bacteria under a fluorescence microscope. Positive findings are usually confirmed by culture or molecular tests.

Auranofin

An oral gold compound formerly used as a disease-modifying drug for rheumatoid arthritis. Today it is studied mainly in research.

Auscultation

Listening to the body with a stethoscope, especially the heart, lungs and bowel.

Auspitz sign

Pinpoint bleeding that appears when a psoriasis plaque is scraped, because the capillaries of the skin papillae lie just below the surface. It is a classic examination sign of psoriasis.

Austin Flint murmur

A low, rumbling heart murmur in diastole at the apex in severe aortic regurgitation. The backflowing jet of blood impedes the opening of the mitral valve.

Autism

A congenital developmental difference involving social communication and perception as well as repetitive patterns of behaviour. The technical term is autism spectrum disorder.

Autoantibody

Antibodies that are mistakenly directed against the body’s own structures. Detecting them helps diagnose autoimmune diseases, although small amounts also occur in healthy people.

Autoclave

A steam sterilisation device that treats instruments and materials with saturated steam under pressure, typically at 121 °C or 134 °C. This reliably kills even resistant bacterial spores.

Autogenic training

A relaxation technique in which a relaxed state is induced through formula-like self-suggestions such as heaviness and warmth. It requires regular practice and is often learned in courses.

Autoimmune disease

A disease in which the immune system attacks the body’s own tissue. Examples include rheumatoid arthritis, type 1 diabetes, multiple sclerosis and Hashimoto’s thyroiditis.

Autoimmune encephalitis

Brain inflammation in which antibodies target nerve cell structures. It presents with memory problems, behavioural changes, seizures or impaired consciousness and often responds well to immunotherapy.

Autoimmune haemolytic anaemia

Anaemia in which the body’s own antibodies tag red blood cells and destroy them prematurely. Warm and cold antibody forms are distinguished; detection is usually by the direct Coombs test.

Autoimmune hepatitis

Liver inflammation in which the immune system attacks liver cells; it responds well to immunosuppressants.

Autoimmune lymphoproliferative syndrome

A congenital disorder of programmed cell death in lymphocytes, usually due to mutations in the FAS gene. It causes enlarged lymph nodes and spleen, autoimmune cytopenias and an increased lymphoma risk.

Autoimmune pancreatitis

A rare form of chronic pancreatitis driven by the immune system that can mimic a tumour. It usually responds well to corticosteroids.

Autoinflammatory disease

A disease in which the innate immune system triggers excessive inflammation without autoantibodies. Recurrent episodes of fever are typical, for example in familial Mediterranean fever.

Autologous stem cell transplantation

Transfer of the patient’s own previously collected and frozen blood stem cells after high-dose chemotherapy. Graft-versus-host disease does not occur, but the anti-disease effect of foreign immune cells is also absent.

Autophagy

The cell’s “self-eating”: breakdown and recycling of damaged cell components. It is stimulated by fasting, among other things, declines with age, and its discovery was honoured with the 2016 Nobel Prize.

Autophony

Unpleasantly loud hearing of one’s own voice and breathing in the ear. Causes include a patulous Eustachian tube or superior semicircular canal dehiscence.

Autoregulation

The ability of organs such as the brain and kidneys to keep their blood flow largely constant despite fluctuations in blood pressure. It works only within certain pressure limits.

AV block

Impaired conduction between the atria and ventricles of the heart that can cause a slow pulse.

AV nodal re-entrant tachycardia

The most common form of paroxysmal racing heart in people with otherwise healthy hearts, caused by a circling impulse in the AV node. Vagal manoeuvres or adenosine end the attack; catheter ablation usually cures it permanently.

AV node

Part of the heart’s conduction system between the atria and ventricles that passes on electrical impulses with a short delay, so the ventricles can fill completely before contracting.

Avacincaptad pegol

A complement factor C5 inhibitor injected into the vitreous to slow the progression of geographic atrophy in dry macular degeneration. It is approved in the USA; vision already lost is not restored.

Avacopan

An oral blocker of the complement C5a receptor given in addition to standard therapy in ANCA-associated vasculitis; it can help reduce corticosteroid use.

Avalglucosidase alfa

A genetically engineered enzyme for enzyme replacement therapy in Pompe disease. It is given by infusion and, thanks to a modified sugar structure, is taken up into muscle cells better than older products.

Avanafil

A PDE5 inhibitor for erectile dysfunction with a relatively rapid onset. It must not be combined with nitrates, as this risks a dangerous fall in blood pressure.

Avapritinib

A targeted inhibitor of altered KIT and PDGFRA kinases used in gastrointestinal stromal tumours with the PDGFRA D842V mutation and in systemic mastocytosis. Brain bleeding and cognitive side effects must be considered.

Avatrombopag

A thrombopoietin receptor agonist in tablet form that stimulates platelet production. It is used in immune thrombocytopenia and before planned procedures in liver disease with low platelets.

Avelumab

A monoclonal PD-L1 antibody from the checkpoint inhibitor group, used among others in Merkel cell carcinoma and as maintenance therapy in urothelial cancer. It can cause immune-mediated inflammation of various organs.

Avoidant personality disorder

A personality disorder with persistent fear of rejection and criticism that leads to withdrawal from social situations. It often overlaps with social anxiety disorder.

AVPU scale

A rapid four-level assessment of consciousness: Alert, responds to Voice, responds to Pain or Unresponsive. It is simpler than the Glasgow Coma Scale.

AWMF

The Association of the Scientific Medical Societies in Germany, the umbrella organisation of German medical societies. It coordinates guideline development and grades guidelines by quality from S1 to S3.

Axenfeld-Rieger syndrome

An inherited malformation of the front part of the eye with changes to the iris and drainage angle, often with dental and facial anomalies. About half of those affected develop glaucoma.

Axicabtagene ciloleucel

A CAR T-cell therapy targeting CD19 for certain aggressive B-cell lymphomas, such as diffuse large B-cell lymphoma.

Axillary artery

The artery continuing from the subclavian artery at the first rib through the armpit, where it becomes the brachial artery. It supplies the shoulder, lateral chest wall and arm.

Axillary gap

Muscle-bounded openings at the back of the armpit through which nerves and vessels pass to the shoulder. The axillary nerve runs through the lateral (quadrangular) space.

Axillary lymph nodes

A group of lymph nodes in the armpit that receive lymph from the arm, breast and upper trunk wall. In breast cancer they are the first station of possible spread and are examined accordingly.

Axis (second cervical vertebra)

The second neck vertebra, with a tooth-like projection (dens) around which the atlas rotates. This allows the head to turn.

Axitinib

A VEGF receptor inhibitor that slows tumour blood vessel growth, used mainly with an immune checkpoint inhibitor in advanced renal cell carcinoma. High blood pressure and diarrhoea are common side effects.

Axon

The long projection of a nerve cell that conducts electrical signals to other nerve, muscle or gland cells.

Axonotmesis

A nerve injury in which the nerve fibres (axons) are interrupted but the connective tissue sheaths remain intact. The fibres can regrow along the sheaths at about one millimetre per day, so spontaneous recovery is possible.

Azacitidine

A drug that inhibits DNA methylation and can thereby reactivate silenced genes in tumour cells. It is used in myelodysplastic syndrome and in acute myeloid leukaemia in older people, often together with venetoclax.

See also: Acute myeloid leukaemia

Azathioprine

An immunosuppressant used in inflammatory bowel disease, autoimmune hepatitis and after transplants. The activity of the enzyme TPMT is often checked before starting, and blood counts and liver tests must be monitored regularly.

Azelaic acid

An anti-inflammatory active ingredient in creams for acne, rosacea and pigmentation spots.

See also: Acne

Azelastine

An antihistamine that acts locally as a nasal spray and eye drops for allergic rhinitis and conjunctivitis. A bitter taste is common; combinations with corticosteroid nasal sprays are available.

Azilsartan

An angiotensin II receptor blocker with relatively strong blood pressure lowering, taken as a prodrug. It is not marketed in Germany but is widely used in other countries.

Azoospermia

Absence of sperm in the ejaculate, due either to impaired production in the testes or to a blockage of the seminal ducts.

Aztreonam

A monobactam antibiotic that acts only against Gram-negative bacteria. It can be used in many patients with penicillin allergy and, inhaled, in cystic fibrosis.

Aztreonam-avibactam

An antibiotic combination of a monobactam and a beta-lactamase inhibitor against multidrug-resistant Gram-negative bacteria. It also works against many organisms with metallo-beta-lactamases and is a reserve antibiotic for severe infections.

Abdominal aortic aneurysm screening

One-off ultrasound examination of the abdominal aorta for early detection of an aneurysm. In Germany, men with statutory health insurance are entitled to it from the age of 65.

Abiotrophia defectiva

One of the so-called nutritionally variant streptococci that grow only on specially enriched culture media. It is a rare cause of endocarditis that is easily missed with standard cultures.

Acanthocyturia

Detection of acanthocytes, red blood cells with blister-like protrusions, in the urine. A proportion above about five per cent indicates bleeding from the glomeruli, for example in glomerulonephritis.

Accessory pancreatic duct

Secondary duct of the pancreas that opens into the duodenum at the minor papilla. In pancreas divisum it takes over the main drainage.

Achromobacter xylosoxidans

Gram-negative environmental bacterium that mainly colonises the airways of people with cystic fibrosis. It is often resistant to many antibiotics and can worsen the course of lung disease.

Acne excoriée

Condition in which spots or tiny blemishes are compulsively squeezed and picked, causing crusts and scars. Besides skin treatment, psychotherapeutic support is often helpful.

Acrokeratosis verruciformis

Rare inherited keratinisation disorder (Hopf type) with flat, wart-like papules on the backs of the hands and feet. It is caused by mutations in the same gene as Darier disease.

Actinic cheilitis

Damage to the lower lip caused by years of sun exposure, with scaling and keratinisation. It is regarded as a precursor of lip cancer and should be treated.

Activin

Signalling protein of the TGF-beta family originally discovered as a promoter of FSH production in the pituitary gland. It also acts on cell growth, inflammation, muscle and blood vessels; the drug sotatercept traps activin-like signals.

Acute phosphate nephropathy

Kidney damage caused by calcium phosphate deposits, usually after sodium phosphate bowel preparations. Older people and those with kidney impairment or on blood pressure medication are particularly at risk.

Acute posterior multifocal placoid pigment epitheliopathy

APMPPE, a rare inflammation at the boundary of retina and choroid in young adults, often after a flu-like infection. Cream-coloured spots appear in the fundus with sudden loss of vision, which usually recovers well.

Adhesive otitis media

Condition in which the eardrum is retracted and stuck to the middle ear cavity after long-standing poor ventilation of the middle ear. It causes conductive hearing loss that can sometimes be improved surgically.

ADTKD

Autosomal dominant tubulointerstitial kidney disease, a group of inherited kidney diseases with slowly progressive loss of function and usually unremarkable urine. In the form caused by uromodulin mutations, gout often appears early.

Afamelanotide

Synthetic analogue of alpha-melanocyte-stimulating hormone given as an implant under the skin. It increases pigmentation and is used in erythropoietic protoporphyria to improve light tolerance.

Afamitresgene autoleucel

Cell therapy in which a patient’s own T cells are genetically equipped with a T-cell receptor against the tumour antigen MAGE-A4. It has been approved in the USA for advanced synovial sarcoma; serious side effects such as cytokine release syndrome are possible.

African tick-bite fever

Common febrile illness caused by Rickettsia africae in travellers returning from southern Africa, for example after safaris. Typical features are fever, headache and often several black scabs at the bite sites; doxycycline works quickly.

Allan-Herndon-Dudley syndrome

X-linked disease caused by deficiency of the thyroid hormone transporter MCT8, so that hormone does not reach nerve cells adequately. Affected boys have a severe developmental disorder together with raised T3 in the blood.

Allantoin

Ingredient in skin care and wound ointments intended to soothe the skin and smooth the horny layer. It is usually well tolerated and is also used in lip and scar care products.

Allergic fungal sinusitis

Chronic sinusitis caused by an excessive immune reaction to fungal spores. Thick, eosinophil-rich secretions and nasal polyps are typical; treatment is surgical and with corticosteroids.

Allostasis

The body’s ability to respond to changing demands by adjusting hormones, circulation and metabolism and so maintain stability. Persistent overload of this system is called allostatic load.

Alternating hemiplegia of childhood

Rare disease, usually caused by mutations in the ATP1A3 gene, with recurrent episodes of one-sided paralysis that can switch sides. It begins before 18 months of age; the paralysis typically disappears during sleep.

Ambient cistern

Space filled with cerebrospinal fluid that wraps around the sides of the midbrain. Its effacement on CT is a warning sign of raised intracranial pressure.

AMPK

AMP-activated protein kinase, a cellular energy sensor that switches on when energy is low. It promotes energy production, for example glucose uptake into muscle, and is activated by physical activity; metformin also acts partly via AMPK.

Anrep effect

Adaptation of the heart to a sudden increase in outflow resistance: after a short time the force of contraction increases, so that stroke volume rises again.

Anterior commissure

Bundle of nerve fibres that mainly connects the two temporal lobes and olfactory regions. In imaging, together with the posterior commissure, it serves as a reference line.

Antibiotic de-escalation

Switching from broad antibiotic therapy to a narrower, targeted agent as soon as the pathogen and its susceptibility are known. It reduces side effects and the development of resistance.

Anticardiolipin antibodies

Autoantibodies against the phospholipid cardiolipin, measured together with lupus anticoagulant and beta-2 glycoprotein antibodies to diagnose antiphospholipid syndrome. An abnormal result must be confirmed after twelve weeks.

Antrochoanal polyp

Benign polyp that usually grows from the maxillary sinus into the posterior nasal opening. It causes one-sided nasal obstruction, often in adolescents.

Apexogenesis

Treatment of a young permanent tooth whose root has not finished growing, in which healthy pulp tissue is preserved. This allows the root to continue growing in length and thickness.

Apple jelly sign

Finding in which a skin lesion pressed with a glass slide appears yellowish-brown and translucent like apple jelly. It indicates a granulomatous infiltrate, for example in lupus vulgaris or cutaneous sarcoidosis.

APRT deficiency

Inherited deficiency of adenine phosphoribosyltransferase in which adenine is converted to poorly soluble 2,8-dihydroxyadenine. This forms kidney stones and crystal deposits in kidney tissue; if detected early, kidney damage can usually be prevented with xanthine oxidase inhibitors.

Aristolochic acid nephropathy

Kidney disease caused by plants of the genus Aristolochia, which were present in some traditional herbal preparations. It leads to rapidly progressive kidney scarring and greatly increases the risk of urinary tract tumours.

Arterial tortuosity syndrome

Rare autosomal recessive connective tissue disease caused by mutations in the SLC2A10 gene. The large arteries are elongated and markedly twisted; narrowing and aneurysms require regular vascular imaging.

Articular disc

Disc of fibrocartilage that divides a joint into two compartments and compensates for irregularities of the joint surfaces. Well-known examples are the discs of the jaw joint and the wrist.

Asboe-Hansen sign

Sign in which an intact skin blister can be extended sideways into the surrounding skin by vertical pressure. It indicates splitting within the epidermis, for example in pemphigus vulgaris.

Ascending colon

Ascending section of the large intestine on the right side of the abdomen, from the caecum to the right colic flexure under the liver. It is here that water is mainly reabsorbed from the gut contents.

Atrophoderma of Pasini and Pierini

Condition with sharply defined, slightly depressed, brownish patches, usually on the back of young adults. It is considered a mild variant of localised scleroderma and is harmless but cosmetically bothersome.

Axon reflex

Reflex in which excitation in a sensory nerve fibre travels not only to the spinal cord but also back into the skin via side branches. Messengers released there widen blood vessels and produce the typical redness around a stimulus.

Back to the Medical Encyclopedia overview

Medical Encyclopedia: A

A-positioning (thoracic positioning)

Aarskog syndrome

Aase syndrome

AAV vector

Abacavir

Abaloparatide

Abatacept

ABCD2 score

ABCDE approach

ABCDE rule

Abciximab

Abdomen

Abdominal angina

Abdominal aorta

Abdominal aortic aneurysm

Abdominal guarding

Abdominal hair loss (liver sign)

Abdominal pain

Abdominal skin reflex

Abdominoperineal resection

Abdominoplasty

Abducens nerve palsy

Abelacimab

Abemaciclib

Aberrometry

Abetalipoproteinaemia

Abfraction

Abiraterone

Abrocitinib

Abscess

Abscopal effect

Absence seizure

ABSI score

Absolute risk reduction

Abstinence

Abulia

Abutment (dental implant)

Acalabrutinib

Acalculia

Acamprosate

Acanthamoeba keratitis

Acanthocytes

Acanthosis

Acanthosis nigricans

Acarbose

Acceptance and commitment therapy

Accessory muscles of respiration

Accommodation (eye)

Accommodative spasm

ACE inhibitor

Aceclofenac

Acemetacin

Acenocoumarol

Aceruloplasminaemia

Acetabular fracture

Acetabulum

Acetazolamide

Acetylator status

Acetylcholine

Acetylcholine receptor antibodies

Acetylcholinesterase inhibitors

Acetylcysteine

Acetylsalicylic acid (aspirin)

Achalasia

Achilles tendinopathy

Achilles tendon

Achilles tendon reflex

Achilles tendon rupture

Achondroplasia

Achromatopsia

Aciclovir

Acidosis

Acinar cells

Acinetobacter baumannii

Acipimox

Acitretin

ACL-RSI scale

Aclidinium bromide

ACMG classification