In the same context, genome-wide association studies (GWAS) using DNA microarray chips showed that the genome regions mostly related to psoriasis development are associated with the immune system, including TNF-α, IL-12B, IL-23R and the human leukocyte antigen Cw6 (HLA-Cw6) of the major histocompatibility complex (MHC) [12]. This evidence concerns the gene TNF and psoriasis.