[Essential thrombocythemia transformed to acute myeloblastic leukemia]

A 48-year-old woman was referred to Tohoku University Hospital in November 1981 because of leukocytosis pointed out in a group examination. At that time white blood cell count was 26.8 x 10(3)/microliters with no blasts, platelet count 268.0 x 10(4)/microliters and hemoglobin 11.4 g/dl. Bone marrow aspirates showed marked increase of megakaryocytes (15,900/microliters). Bone marrow chromosome analysis revealed 46, XX, -18, +mar without Ph1 chromosome, and DNA analysis showed no bcr rearrangement. She was diagnosed as having essential thrombocythemia and was treated with busulfan. On November 1986, she developed remarkable leukocytosis with leukemic blasts. White blood cells reached 153 x 10(3)/microliters with 33% blasts. Her blasts were positive for peroxidase staining, but negative for platelet peroxidase on electron microscopic study and platelet specific glycoproteins. A diagnosis of acute myeloblastic leukemia (M2) was made. The patient received various combination chemotherapy, which was ineffective, and she died due to pneumonia on June, 1989. In Japan, there has been reported only 8 cases of essential thrombocythemia transformed to acute leukemia. The clinical pictures of these 9 cases were discussed.