[Pathogenesis of psoriasis].

Psoriasis is a polymorphous disease. The multiple ways to combine susceptibility genes, immunological mechanisms and modifying factors which interact toward the development of the lesions contribute widely to this polymorphism. It is elusive to look for the source of the disease in an exclusive disorder of the immune system or in an isolated primitive change of the epithelial or stromal skin cells. It is more likely that various combinations of selective abnormalities of these two compartments give raise to the psoriatic phenotype. Indeed, if in on hand T-cells are essential in the development of psoriatic plaques, the role of innate immunity in this process is better recognized, and numerous psoriasis susceptibility genes are linked to immunity, on the other hand some susceptibility factors related to primitive abnormalities of keratinocytes and some of the most recent murine models of psoriasis are based on modifications targeted to the keratinocytes. This article makes a current point on the physiopathology of the disease.