Blastic transformation of essential thrombocythemia. A case report.

A case of blastic transformation of essential thrombocythemia (ET) is reported. A 69-year-old male was first admitted to hospital because of fever in February, 1982. He was diagnosed as having ET because of marked thrombocytosis (205.5 x 10(10)/1), absence of erythrocytosis, absence of splenomegaly, normal karyotype and no increment of blasts in the bone marrow, and normal levels of neutrophil alkaline phosphatase, vitamin B12 and folate. He was treated with busulfan, and subsequently his platelet count was well controlled for about five years. At the second admission, blasts were present in the peripheral blood, and later accounted for 49% of the total leukocyte count. Histological examination of a bone biopsy specimen showed homogeneous proliferation of blastic cells and slight reticulin fibrosis. At autopsy, the degree of bone marrow fibrosis had increased. This was considered to be a very rare case of ET with blastic transformation in the terminal phase.