Even patients with psoriasis and PsA have significant genetic susceptibility linked to the MHC (Mayor Histocompatibility Complex) locus (HLA-C(*)06:02), but other genes are also involved, especially those related to cytokine production, the IL-17/IL-23 axis, and the NF-kB and type 2 T helper pathways, which are strongly associated with IBD as well [16]. This evidence concerns the gene IL23A and inflammatory bowel disease.