Thrombocythemia (high platelet count)

My wife has been diagnosed with essential thrombocythemia — yet she has no symptoms. What causes essential thrombocythemia?

- Mike / United Kingdom

Mayo Clinic hematologist Ruben Mesa, M.D., and colleagues answer select questions from readers.

Answer

Thrombocythemia refers to a high platelet count. Platelets (thrombocytes) play an important role in blood clotting. The term "essential thrombocythemia" means that the cause of a high platelet count can't be determined.

A normal platelet count ranges from 150,000 to 450,000 platelets per microliter of blood. In very large numbers — exceeding 600,000 platelets per microliter — platelets may cause clotting in blood vessels and abnormal bleeding.

A doctor may diagnose essential thrombocythemia by blood tests that show a sustained increase in platelets not due to another condition, such as polycythemia vera or chronic myelogenous leukemia. In some cases, thrombocythemia is due to a specific genetic mutation.

Some people with thrombocythemia have no signs or symptoms. Others may experience bleeding from the nose or gums, blood clots, heart attack or stroke. When needed, treatment may include:

Low-dose aspirin to reduce clotting risk
Medications such as interferon or hydroxyurea (Hydrea, Droxia) to lower platelet counts in those individuals who are older than age 60, are at high risk of heart disease or have a history of abnormal bleeding or blood clots