Although rs2476601 (R620W) in PTPN22 has been constantly associated with RA in populations of European descent, including US [31], UK [32], Finnish [33], Swedish [34], German [35], Dutch [36], Spanish [37], and Canadian [38] populations, this SNP did not show a significant association with RA in the Japanese population [39] studied because there is a very low minor allele frequency in this population. The gene discussed is PTPN22; the disease is rheumatoid arthritis.