Outside the major histocompatibility complex (MHC), PTPN22, TRAF1/C5, and TNFAIP3 loci were the most consistently associated with susceptibility and TRAF1/C5 region also with RA severity [10, 11] and noncardiovascular mortality in some populations [12]. Here, PTPN22 is linked to rheumatoid arthritis.