Efficacy of imatinib mesylate (STI571) treatment for a patient with rheumatoid arthritis developing chronic myelogenous leukemia.

We report on an 80-year-old man with rheumatoid arthritis (RA) who presented with chronic myelogenous leukemia (CML). Five years after the onset of RA, the CML diagnosis was made. The patient was treated for CML with 300 mg of imatinib mesylate (STI; signal transduction inhibitor 571) for 8 weeks. Laboratory tests showed that the C-reactive protein level, percentage of cells exhibiting the Philadelphia chromosome (Ph1), WBC count, and Lansbury index for RA all dropped respectively from 7.5 mg/dl to 1.0 mg/dl, 74.9% to 1%, 25, 100/microl to 9900/microl, and 51% to 14%. Administration of imatinib mesylate is felt to be effective in treating not only CML but also RA in the active stage.