Pharmacological management of essential thrombocythemia

Two factors have deeply influenced the area of essential thrombocythemia (ET). A gain-of-function mutation in the pseudokinase region of the JAK2 gene, which partly explains the pathophysiology of myeloproliferative neoplasms (MPNs), was discovered in 2005 and is present in 50 - 60% of ET patients. Furthermore, the 2008 WHO MPN classification outlined criteria for the separation of ET and early or prefibrotic primary myelofibrosis (PMF). However, these and other new findings have not yet changed the pharmacotherapy of ET, which is based on risk stratification for thrombohemorrhagic risk and aims to reduce thrombosis and bleeding.

Studies on the basis for and the validation of the WHO classification as well as studies on possible new risk factors are covered. The most important drugs for ET treatment and consensus recommendations for management of ET are also presented.

The new WHO classification should be used for both ET studies and clinical practice, since true ET has a different prognosis than early PMF. The management of patients should be based on risk stratification. Age > 60 years or previous throbosis (high risk) and platelet counts > 1500 × 10(9)/l warrant cytoreductive treatment, and high risk patients and selected low risk patients should be given anti-aggregation therapy.