Acute Megakaryoblastic Leukemia Developing as Donor Cell Leukemia after Umbilical Cord Blood Transplantation.

A 64-year-old man with acute myeloid leukemia underwent umbilical cord blood transplantation (UCBT). After 11 months of complete remission (CR) following UCBT, the bone marrow showed 7.5% myeloblasts. CR was obtained after a single course of azacitidine monotherapy, but the myeloblasts gradually increased in the blood. We made a diagnosis of acute megakaryoblastic leukemia derived from donor cell with a fluorescence in situ hybridization (FISH) analysis of the sex chromosomes and an immunophenotypic analysis. Azacitidine was administered again and produced a therapeutic effect of stable disease. This case suggests that azacitidine may be a useful therapy for patients with acute megakaryoblastic leukemia in situations in which intensive chemotherapy and transplantation are not indicated.