Thrombocythemia (high platelet count)
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
Essential thrombocythemia is a stem cell disease; "essential" means that the cause is unknown. Blood cells, including red blood cells (which carry oxygen from the lungs to the rest of the body), white blood cells (which fight infections) and platelets (which form blood clots) are produced from stem cells in the bone marrow. The stem cells grow and divide into intermediate cells and finally into mature cells in the blood. A problem with the stem cell can lead to problems with all other cells. ET is a stem cell disease that leads to an overproduction of platelets (thrombocytes) without other secondary causes, sometimes with an accompanying increase in white blood cells.
Blood platelets help prevent and control bleeding resulting from injury to blood vessels. The term thrombocythemia refers to an unusually high platelet count. A normal count ranges from 150,000 to 450,000 platelets per microliter (mL) of blood. When the platelet count exceeds 600,000 platelets per mL, doctors call this essential thrombocythemia. Most young people with essential thrombocythemia have no signs or symptoms.
ET is classified as a chronic myeloproliferative disorder (CMPD). The CMPDs also include polycythemia vera, agnogenic myeloid metaplasia with myelofibrosis, and chronic myelogenous leukemia.