Statistically significant differences were found in the distributions of the MTHFR 1298A > C, TYMS 3'-UTR−6 > +6, RFC1 80 G > A, FPGS 1994 G > A, GGH 452 C > T, ABCB1 3435 C > T, ABCC2 IVS23 + 56 T > C, and ABCG 914 C > A alleles in RA patients between our Japanese population and Caucasians (Table 2). Here, TYMS is linked to rheumatoid arthritis.