The Management of Essential Thrombocythaemia

Essential thrombocythemia (ET) is a clonal myeloproliferative disorder with a relatively benign clinical course and long survival in most patients. The major cause of mortality and morbidity are thromboembolic complications, which occur more frequently in older subjects or in those with a previous thrombosis. The therapeutic options comprise cytoreductive agents (cytotoxic drugs, interferon, anagrelide) and anti-aggregating drugs. In clinical practice the choice of treatment primarily takes into account the patient's age, history and symptoms. The use of platelet-lowering agents is indicated in patients above 60 years and in those with a history of thrombosis or major bleeding, or very high platelet count (e.g. >1,000 X 10(9)/1). Hydroxyurea has emerged as the treatment of choice after the recent demonstration of its efficacy in reducing not only the platelet count but also thromboembolic complications. Low-dose aspirin may be added in the presence of thrombosis or microvascular disturbances. In younger, asymptomatic patients, an initial policy of observation, without specific treatment, or with only low-dose antiaggregating agents seems reasonable. Doubt about the risk of leukaemia transformation associated with hydroxyurea suggests that the use of interferon or anagrelide should be explored.