In addition to the HLA region, non-HLA gene polymorphisms, including PTPN22 rs2476601 (5, 22), STAT4 rs7574865 (23, 24), TRAF1/C5 rs3761847 (25, 26), CTLA4 rs3087243(27, 28) and PADI4 rs2240340 (6, 29), have also been reported to be strongly associated with RA susceptibility. This evidence concerns the gene PADI4 and rheumatoid arthritis.