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A myeloproliferative neoplasm characterized by extreme thrombocytosis. Approximately 50% of essential thrombocythemia cases are characterized by presence of the JAK2 mutation. See thrombocytosis.
essential thrombocythemiaEssential thrombocytosis Hematology A primary myeloproliferative disorder of older–age 55-75–adults, or less commonly of young ♀, with a platelet count is > 600 x 109/L; ET has many clinical features of P vera; it affects the same age group, is accompanied by splenomegaly, has similar BM findings, intensity of leukocytosis Diagnosis Polycythemia Vera Study Group criteria Treatment Hydroxyurea, a myelosuppressant, prevents recurrent thromboses. See Polycythema vera.
Essential thrombocythemia-diagnostic criteria
1. Platelets > 1 x 109 /L (US: < 1000/mm3)
2. Hb < 2.05 mmol/L (US < 13.0 g/dL)
3. Iron in BM or if absent, little ↑ in Hb after 1 month of oral iron therapy
4. Absent marrow fibrosis by biopsy and
5. Absent Philadelphia chromosome
Polycythemia Vera Study Group