MTHFR and rheumatoid arthritis: The authors examined the same MTHFR gene rs1801131 and rs1801133 SNP polymorphism; for rs1801133 SNP no the genetic polymorphism did not associate with MTX treatment response, while the TT genotype of rs1801131 was associated with a good response76, their findings are best applied to patients with early RA who have not received DMARDs.