Psoriasis: the epidermal component.

Besides the infiltrate of immune cells in psoriatic lesions, the principal characteristic changes in the skin are changes of the epidermal architecture and alterations of keratinocyte differentiation, which are distinct from other inflammatory skin diseases clinically and histologically. Several lines of evidence suggest that 3 of the 9 psoriasis susceptibility loci identified today might play a role in the keratinocyte differentiation program. Therefore, besides the dysregulation of the immune system, intrinsic epidermal components are also likely to play a role in triggering and/or sustaining the disease process and contribute to the chronicity of psoriasis and its frequent relapses.