Rheumatoid arthritis (RA) is a chronic, systemic inflammatory disorder of unknown etiology. Inflammation may usually extend beyond the joints and involve other organs. Clinically detectable splenomegaly is present in 5∼10% of RA. Methotrexate (MTX) is a structural analog of folic acid that inhibits the enzyme dihydrofolate reductase, so cellular proliferation is reduced. MTX has been proven to be effective in treating RA and is believed to be nononcogenic at low, weekly dose employed in the patients with RA. However, recently there has been increased concern about the oncogenic potential of MTX because of several case reports describing the occurrence of non-Hodgkin's Lymphoma (NHL) in the patients with RA treated with MTX. A 65-year-old woman with RA was treated with low dose MTX (i.e. 10 mg/week) for 3 years. Because of prolonged left upper abdominal pain and thrombocytopenia associated with huge splenomegaly, splenectomy was performed. Biopsy revealed splenic B-cell NHL. We report a case of RA with splenomegaly who developed B-cell NHL in spleen during low dose MTX therapy.

Keywords: Rheumatoid arthritis, B-cell non-Hodgkin's lymphoma, Methotrexate, Splenomegaly