Thirty two year-old woman showed severe anemia, mild leukopenia with 2.5% blasts, and normal platelet count. A bone marrow aspirate revealed a normo-cellular marrow with 22% blasts and 26.8% erythroblasts, and dyshematopoiesis involving three cell lines was observed. Some of the blasts were positive for platelet peroxidase stain, and numerous micromegakaryocytes were seen in both bone marrow and peripheral blood. However, platelet functions were normal. Cytogenetic analysis showed -7, +der (1) t(1;7)(p11;p11), t(3;3)(q21;q26). She was diagnosed as de novo myelodysplastic syndrome (RAEB-T) and treated with low-dose cytosine arabinoside. Without hematological improvement, she progressed to overt leukemia. At the time of overt leukemia, the blasts were negative for peroxidase stain, and chromosomal abnormalities were evolved to -7, t(1;7;8)(p31.2;q36;p21), t(3;3)(q21;q26.2).
