Acute leukemia after azathioprine treatment of connective tissue disease.

A 23-year-old man is reported who had a connective tissue disorder with features of rheumatoid arthritis and systemic lupus erythematosus. Because of the development of severe myocarditis and acute cerebral dysfunction treatment with azathioprine and prednisone was instituted, with dramatic clinical improvement. Ten months later, when a total of some 52 g of azathioprine had been administered, acute myelomonocytic leukemia developed. Although acute myelogenous leukemia has been noted in several individuals receiving immunosuppressive drugs for treatment of lymphoreticular neoplasms, this complication has heretofore been rare in patients given azathioprine for non-neoplastic disease. The present case is documented because of the increasing use of immunosuppressive drugs in treatment of various rheumatic disorders and the need to establish the relationship, if any, between the use of such agents and malignancy.