The three variants of the ATIC gene analyzed in the present study were selected for their possible biological significance and include one missense variant (rs2372536) and two intronic variants (rs4673990 and rs4673993) involved in altering the structure and function of the encoded protein; however, other variants of the ATIC gene, which may be associated with the response to treatment with MTX in patients with RA, should also be analyzed, even at the level of protein expression, using another methodology such as flow cytometry. This evidence concerns the gene ATIC and rheumatoid arthritis.