PTPN22 and rheumatoid arthritis: PTPN22 is a known immune regulator gene and this particular variant (rs2476601 A allele) has been associated with an increased risk of several autoimmune diseases, including rheumatoid arthritis, systemic lupus erythematosus, vitiligo, autoimmune thyroid conditions, type 1 diabetes, and others (Supplementary Data 2, 3 and Supplementary Fig. 3).