In addition, genome-wide association studies have implicated several other psoriasis associated genes, involved in various biological processes, including IL-23/IL-17 pathway [83,85–89], MHC class I processing [89,90], epidermal cell differentiation [90,91], NF-κB signalling [83,89,92], ubiquitin pathway [90,93], Th2-type response [83] as well as genes of yet unknown function [94]. This evidence concerns the gene IL23A and psoriasis.