Thrombocytosis and essential thrombocythemia

Management of essential thrombocythemia (ET) starts with confirming the accuracy of the diagnosis and excluding congenital and reactive thrombocytosis and myeloid neoplasms which might mimic ET. Diagnosis acording to WHO criteria requires a platelet count of ≥450×109/L, presence of one of the three “driver” mutations, including JAK2, CALR, and MPL or in their absence the exclusion of other causes of thrombocytosis, and bone marrow histology. Most patients with ET have a normal life expectancy with low risk of leukemic transformation or fibrotic progression. Observation alone remains a viable treatment option for “very low-risk” patients while all other patients might benefit from aspirin therapy, in a once- or twice-daily schedule. In addition, cytoreductive treatment is recommended in patients with thrombosis history, and drugs of choice in this regard are hydroxyurea and pegylated interferon-α. There is currently no evidence to support the need for JAK inhibitor therapy in the majority of patients with ET, regardless of whether or not they are hydroxyurea-refractory.