Rheumatoid arthritis (RA) is a major cause of adult chronic inflammatory arthritis and an autoimmune disease of unknown etiology in which the inflammatory pathology involves T cell activation. Genetic mutations in the Mediterranean fever (MEFV) gene, encoding pyrin, influence the severity of RA, but the underlying mechanisms are not completely understood. In this study, we investigated whether the full-length MEFV gene (MEFV-fl) and the exon 2-deleted splice isoform (MEFV-d2) expression are associated with or responsible for the clinical conditions of RA. This study include 47 patients with RA and 47 age- and gender-matched healthy controls. Quantitative real-time polymerase chain reaction analysis was performed to examine transcriptional changes in MEFV gene expression from peripheral blood samples. Reverse transcription-polymerase chain reaction of peripheral blood cells revealed the downregulation of MEFV-fl mRNA in non-treated patients compared with healthy controls and treated patients. MEFV-d2 expression was not different between groups. This is the first study to investigate the expression of MEFV transcript in RA. Deregulation of the MEFV gene is likely to result in uncontrolled inflammation as observed in RA. Therefore, downregulation of MEFV-fl may be involved in the pathogenesis of early-stage RA and treatment and may ameliorate MEFV-fl expression.