[How to understand psoriasis?].

Recent advances in the treatment of psoriasis have led to improve understanding in the pathogenesis of the disease. Skin lesions are scaling erythematous plaques. Although initially considered as a disease of epidermal cells, it is now widely accepted that the epidermal abnormalities, which are characteristic of the disease, are secondary to the development of a skin inflammation. Psoriasis is an autoimmune disease due to the activation in the skin of antigen-specific T cells leading to release of cytokines that results in proliferation of keratinocytes. However, the autoantigen(s) is (are) yet unknown. Several new biological treatments have been developed, which target specific steps in the pathophysiology of the disease.