Methylenetetrahydrofolate reductase and reduced folate carrier-1 genotypes and methotrexate serum concentrations in patients with rheumatoid arthritis

Abstract

We investigated the genotypes of methylenetetrahydrofolate reductase (MTHFR) and reduced folate carrier-1 (RFC-1), and the serum concentrations of methotrexate (MTX) in 100 outpatients with rheumatoid arthritis (RA). Frequencies of MTHFR C677T and A1298C were similar to those reported in Japanese RA patients, while frequencies of RFC-1 G80A genotypes differed from those reported in RA patients in the United States. No correlations were found between these genotypes and serum MTX levels.