Myelomegakaryoblastic transformation of essential thrombocythemia.

Essential thrombocytherrlia, considered one of the least common of the myeloproliferative disorders, is being diag nosed more frequently with the increasing use of automated blood cell counters. Essential thrombocythemia described by Epstein and Goendel in 1934 is a diagnosis of exclusion i.e., exclusion of all sy stemic conditions associated with thrombocytosis in an individual with a persistently elevated platelet count of more than 600x10/L (600,000/ul). Prognosis of essential thrombocytherrlia is excellent, with a median survival in excess of 10 years. However, 10 percent of cases undergo blastic transformation. A case of essential thrombocythemia presenting in myelomegakaryoblastic transfomlation is reported, due to its rare occurence and presentation.