Essential Thrombocythemia

Essential Thrombocythemia is a myeloproliferative neoplasm characterized by sustained elevated platelet counts (typically greater than 450,000 per microliter) resulting from clonal proliferation of megakaryocytes in the bone marrow. The disease occurs in three major genetic subtypes: JAK2-positive (50-60%), CALR-positive (20-30%), and MPL-positive (5-10%), with the remaining cases being 'triple-negative.' These mutations drive uncontrolled megakaryocyte proliferation independent of normal growth signals. The elevated platelet count paradoxically increases both thrombotic risk (blood clots) and hemorrhagic risk (bleeding), due to both quantitative increases in platelets and qualitative functional abnormalities. Many patients are asymptomatic and discovered incidentally on routine blood work. Symptomatic patients may experience headaches, dizziness, visual disturbances, and thrombotic or hemorrhagic events. Microvascular thrombosis can cause painful burning sensations in extremities (erythromelalgia). Long-term complications include arterial and venous thrombosis, and transformation to secondary myelofibrosis or acute leukemia in approximately 5-10% of patients.