[Essential thrombocythemia that transformed to myelofibrosis after three years]

A 66-year-old man was presented with thrombocytosis in February, 1988. Laboratory examinations on admission revealed a white blood cell count of 17,700/microliters and a platelet count of 274.4 x 10(4)/microliters. Bone marrow aspirates showed an increase of megakaryocytes (1,294/microliters). There was no fibrosis or Ph1 chromosome. He was diagnosed as having essential thrombocythemia and was treated with thrombopheresis, carboquone and ranimustine (MCNU). Subsequently his platelet count was well controlled approximately for three years. He was readmitted because of pyrexia and left hypochondralgia in February 1991. Physical examination revealed hepatosplenomegaly. Peripheral blood revealed leukoerythroblastosis associated with the occurrence of tear drop cells. Bone marrow aspiration resulted in a dry tap and the biopsy specimen showed reticulin fibrosis. This is a fairly rare case of essential thrombocythemia that transformed to myelofibrosis.