It has been found that MTX response in RA patients is associated with such genetic variants as 1298A > C (rs1801131) in MTHFR [15, 16], 80G > A (rs1051266) in RFC-1 [17], rs2838956A > G and rs7499G > A in SLC19A1 [18]. The gene discussed is SLC19A1; the disease is rheumatoid arthritis.