Essential thrombocythemia

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Essential thrombocythemia is a myeloproliferative neoplasm in which excess platelets are produced, leading to abnormal blood clotting or bleeding.

The hands and feet may burn, turn red, and tingle, and the fingertips may feel cold.
Blood tests usually provide a diagnosis, but sometimes a bone marrow biopsy is needed.
Treatments that suppress symptoms and decrease platelet production are given.

In myeloproliferative neoplasms. the blood-producing cells in the bone marrow (precursor cells, also called stem cells) develop and reproduce excessively.
Platelets (thrombocytes) are cell-like particles in the blood that help the body form blood clots. Platelets are normally produced in the bone marrow by cells called megakaryocytes. In thrombocythemia, megakaryocytes increase in number and produce too many platelets. Thrombocythemia can be

Primary (essential): Caused by a disorder of platelet-forming cells
Secondary: Caused by a disorder that triggers increased production by normal platelet-forming cells (see secondary thrombocythemia)

Essential thrombocythemia usually occurs in people over age 50. Sometimes younger women are affected.
Essential thrombocythemia is considered a myeloproliferative neoplasm, in which certain blood-producing cells in the bone marrow develop and reproduce excessively. The cause of is a genetic mutation usually in the Janus kinase 2 (JAK2), thrombopoietin receptor (MPL), or calreticulin (CALR) genes. The JAK2 gene mutation causes increased activity of the JAK2 enzyme, a protein that causes excess cell production. The MPL and CALR mutations also increase the activity of JAK2 enzyme, leading to increased blood cell production.