The pathogenesis and genetics of psoriasis.

Psoriasis vulgaris and psoriatic arthritis are interrelated disorders with an important genetic component. While linkage studies have identified several candidate loci and genes, only recent technological advances and extensive genome-wide association studies have provided robust evidence of associations between psoriasis and several genes inside and outside the major histocompatibility complex. Most of these genes can be incorporated into an integrated pathogenic model of psoriatic disease comprising distinct signaling networks affecting skin barrier function (LCE3, DEFB4, GJB2), innate immune responses involving nuclear factor-κB signaling (TNFAIP3, TNIP1, NFKBIA, REL, FBXL19, TYK2, NOS2, CARD14), and adaptive immune responses involving CD8 T cells and interleukin 23 (IL-23)/IL-17-mediated lymphocyte signaling (HLA-C, IL12B, IL23R, IL23A, TRAF3IP2, ERAP1). A better understanding of the potential gene/gene and gene/environment interactions and of the functions of altered transcripts will undoubtedly have nosologic, therapeutic and prognostic implications.