Medical Encyclopaedia › Psoriasis (short definition)
In brief: Psoriasis is a chronic inflammatory, non-contagious disease that mainly affects the skin. Typical features are sharply demarcated, red plaques with silvery-white scales.
Causes
In psoriasis, the immune system is misdirected: messenger substances such as interleukin-17 and -23 drive inflammation that causes skin cells to renew themselves at a greatly accelerated rate. A hereditary predisposition is common. Flare-ups can be triggered by infections (e.g. streptococci), skin injuries, stress, smoking, alcohol and certain medicines.
Forms
The most common form is plaque psoriasis on the elbows, knees, scalp and sacrum. There are also guttate, pustular and inverse forms in skin folds, as well as nail changes such as pitting or oil-drop discoloration.
More than a skin disease
In up to a third of those affected, the joints also become inflamed (psoriatic arthritis). In addition, overweight, diabetes, high blood pressure, cardiovascular disease and depression occur more frequently. Psoriasis is therefore regarded today as a systemic inflammatory disease.
Treatment
Mild forms are treated topically with corticosteroids, vitamin D derivatives (e.g. calcipotriol) or a combination of the two. For moderate to severe psoriasis, phototherapy and systemic medicines such as methotrexate, apremilast or biologics against TNF, IL-17 or IL-23 may be considered. The choice depends on severity, associated conditions and life situation and is made by a doctor. Emollient care and keratolytic preparations support treatment.
When to see a doctor?
Dermatological advice is advisable for new skin lesions, extensive involvement, involvement of the nails or scalp, joint pain or morning stiffness, and if the current treatment is not sufficient.
Related terms in the encyclopaedia
Psoriatic arthritis, Biologics, Methotrexate, Secukinumab, Risankizumab, Corticosteroids, Autoimmune disease
Sources
- Deutsche Dermatologische Gesellschaft (DDG) und Berufsverband Deutscher Dermatologen (BVDD): S3-Leitlinie Therapie der Psoriasis vulgaris, AWMF-Register 013-001
- IQWiG: gesundheitsinformation.de – Gesundheitsinformationen des Instituts für Qualität und Wirtschaftlichkeit im Gesundheitswesen
Note: This article is for general information and does not replace advice, diagnosis or treatment from a doctor or pharmacist. Last updated: October 2026.