A total of 4 haplotypes (CA, CC, TA, TC) were constructed for the two SNP loci of the MTHFR gene, but there was no statistically significant difference in these 4 haplotypes between the RA group and the healthy control group (χ2total = 2.324, p = 0.312, df = 2), see Table 9. The gene discussed is MTHFR; the disease is rheumatoid arthritis.