Although the IL-23/Th17 pro-inflammatory axis is closely linked to development of psoriasis, psoriatic arthritis and rheumatoid arthritis, a substantial role for IL-17A/F cytokine and IL-17RA in intestinal inflammation such as inflammatory bowel disease and Crohn ́s disease has been documented [43,44]. The gene discussed is IL17RA; the disease is psoriatic arthritis.