[Psoriasis: a chronic skin disease].

Psoriasis is a frequent chronic inflammatory skin disease. Physiopathological mechanisms are still partially unclear. Psoriasis results of the influence of environmental factors on a complex genetic background. Clinical presentations are various, from the classical erythematous plaques-type to the pustulosis forms. Psoriasis can be associated with some other inflammatory diseases like psoriatic arthritis and Crohn's disease. Considered for long as a benign entity, psoriasis can significantly impair patient's quality of life. Some serious forms like generalized erythrodermia and generalized pustulosis can affect the vital prognosis. The treatment of the patient requires a slight collaboration between the patient, the dermatologist and the attending physician.