A 62-year-old male developed pancytopenia due to severe hypocellular marrow. He was initially diagnosed with aplastic anemia (AA), and was treated with antilymphocyte globulin (ATG), cyclosporine (CyA), and granulocyte colonystimulating factor (G-CSF). However, 3 days after starting the therapy, the leukocyte count increased abruptly and the bone marrow became markedly hypercellular with hypergranulated promyelocytes. Cytogenetic analysis demonstrated t(15
acute promyelocytic leukemia
hypoplastic marrow