PTPN22 and rheumatoid arthritis: Additionally, a relationship between two functional genetic variants located in the PTPN22 gene (PTPN22 rs2476601 (R620W) and PTPN22 rs33996649 (R263Q)) and some inflammatory diseases (such as type I diabetes, systemic lupus erythematosus and rheumatoid arthritis) has been demonstrated in Caucasians [6, 10, 11].