Clin. lab. Haemat. zyxwvut 1994, zyxwv 16, 285-289 zyxwv CASE REPORT Therapy-related acute myeloid leukaemia following immunosuppression with azathioprine for polymyositis KOYAMANGALATH KRISHNAN*, PAUL ADAMS*, SCOTT SILVEIRA?, SUSAN SHELDON? zyxw & LYUBICA DABICH* *Division zyxwvu of Haematology-Oncology, Department of Internal Medicine and ?Department of Pathology, University of Michigan Medical School, Ann Arbor, MI, zyxw USA Accepted for publication 16 May 1994 Summary A 52-year-old man developed therapy-related acute myeloid leukemia (AML) following prolonged immunosuppression with azathioprine for polymyositis. Karyotypic analysis showed deletions of the short arm of chromosome 7 and the long arm of chromosome 5. The importance of recognizing this potential complication while treating benign rheumatological and immunological diseases with purine analogues like azathioprine is emphasized. Therapy-related AML is a poor prognostic group that does not respond favourably to standard induction therapy. Keywords: polymyositis, azathioprine, acute myeloid leukaemia Therapy-related acute myeloid leukaemia is a well recognized complication following cytotoxic therapy with alkylating agents (cyclophosphamide, busulfan, chlorambucil, melphalan and nitrogen mustards) in various malignant and benign conditions (Louie & Schwartz 1978; Frisch, Bart1 & Chaichik 1986). Rarely, purine analogues like azathioprine have been known to cause lymphomas, solid tumours and acute myeloid leukaemia in patients on long-term immunosuppres- sion for various conditions like primary biliary cirrhosis (Louie et al. 1978), rheumatoid arthritis (Seidenfeld et al. 1984), systemic lupus erythematosus (Vasquez et al. 1992), systemic sclerosis (Tulliez et al. 1974) and renal transplant recipients (Hoy, Packman & Freeman 1982). We report a case of acute myeloid leukaemia following treatment of poly- myositis with azathioprine. Correspondence: Dr K. Krishnan, Division of Haematology-Oncology, Upjohn Center, I3 10, E. Catherine Drive, Ann Arbor, Michigan 48 109-0504, USA. 285