Association of C35T polymorphism in dihydrofolate reductase gene with toxicity of methotrexate in rheumatoid arthritis patients

Background: Methotrexate (MTX), a folate analogue, is the most commonly used disease-modifying drug in the treatment of rheumatoid arthritis (RA). However, high interindividual differences in drug response are present among RA patients.Research design and methods: In a group of 234 RA patients treated with MTX, we investigated whether rs1650697 polymorphism in DHFR gene may have an impact on MTX efficacy and/or adverse drug effects (ADEs). Relative DAS28 values (rDAS28) were used for the estimation of MTX therapy and all ADEs were recorded. Patients were genotyped for selected polymorphism by real-time PCR method. Results: According to the European League Against Rheumatism criteria after 6 months of MTX therapy, 196 patients (83.8%) were classified as responders (25 (10.7%) were good and 171 (73.1%) were moderate) and 38 patients (16.2%) as nonresponders. ADEs were observed in 55 patients (23.5%). Conclusions: Our results showed that the presence of T allele might be protective against MTX hepatotoxicity measured by transaminase levels (p = 0.05). Furthermore, among patients who also received low-dose corticosteroids, we have found a lower rDAS value in patients with CC genotype (p = 0.039).