Acute leukemia after low dose methotrexate therapy in a patient with rheumatoid arthritis.

An 83-year-old woman with seropositive rheumatoid arthritis (RA) developed acute myeloid leukemia after receiving weekly methotrexate (MTX) for 33 months (total dose 690 mg). Although cytogenetic abnormalities typical of damage by cytotoxic agents were not documented, our case may be the first report of acute myeloid leukemia in RA with MTX. We estimate that 6 similar cases should have been observed in France by chance alone. The absence of other reports suggests either that MTX possesses a paradoxical protective effect or that it is not considered a risk factor for malignancy by rheumatologists. Since the number of patients with RA taking MTX can be estimated with reasonable accuracy, the reporting of all suspected cases could help to assess the safety of the drug in rheumatology.