Curriculum · Hematology
Essential thrombocythaemia
What it is
Essential thrombocythemia is a myeloproliferative disorder in which the platelet count is increased. It is diagnosed only after other myeloproliferative disorders and reactive thrombocytosis have been excluded.
How it presents
Vasomotor symptoms are the commonest group (40%). Headache is common, and dizziness and syncope also occur. Erythromelalgia gives burning pain of hands and feet, usually worse with heat, and is caused by platelet activation.
- Thrombosis, both arterial and venous
- Bleeding, often GI
- Constitutional symptoms and splenomegaly
How it is diagnosed
The CBC shows increased platelets. JAK2 molecular testing comes first; if it is negative, test for CALR and MPL mutations.
Bone marrow is normocellular or hypercellular, with megakaryocytic hyperplasia and giant megakaryocytes showing staghorn nuclei. The diagnosis is then made by excluding other myeloproliferative disorders and reactive thrombocytosis.