[A case of rheumatoid arthritis with malignant lymphoma taking methotrexate].

We describe one case with rheumatoid arthritis who developed non-Hodgkin's lymphoma during treatment with low dose weekly methotrexate. A 73 year-old man had seropositive RA since 1974. He had been treated with several medications, including nonsteroidal antiinflammatory drugs, gold sodium thiomalate (from January, 1987), and bucillamine (from January, 1988). He presented to this hospital in April 1988, at a time when his rheumatoid arthritis worsened. Methotrexate was administered at a weekly dose of 7.5 mg orally, together with a daily dose of 5 mg of prednisone. He had had no joint-related pain and no side effects until December 1991 (total dose 1290 mg) when severe abdominal pain was started abruptly. The chest X-ray showed an abdominal free air and a diagnosis of acute panperitonitis was made. An emergency operation was carried out. There was a soft-tissue mass in the terminal of ileum which was ruptured with massive ascites. Histologic examination of the mass revealed a diffuse large cell lymphoma. The oncogenic potential of MTX and rheumatoid arthritis is reviewed.