Acute myeloblastic leukemia following prolonged treatment of Crohn's disease with 6-mercaptopurine

A 65-year-old man with Crohn's disease died of acute myeloblastic leukemia after treatment for 11.8 years with 6-mercaptopurine, 1.5 mg/kg/day (100 mg/day). On cytogenetic analysis, most of the malignant bone marrow cells had deletion of chromosome 7, the most frequently reported cytogenetic abnormality in chemotherapy-related acute leukemia. This finding, together with previous reports of acute leukemia and other malignancies following prolonged treatment with azathioprine or 6-mercaptopurine for nonmalignant conditions including inflammatory bowel disease, indicates that long-term use of these drugs for inflammatory bowel disease may increase the risk of malignancy. However, the magnitude of the risk is unknown.