Essential thrombocytosis (also called essential thrombocythaemia) is a condition where the bone marrow produces too many of the cells called platelets. Platelets are cells that are responsible for blood clotting and so essential thrombocytosis is associated with an increased risk of blood clotting - but also bleeding is some cases.
Essential Thrombocytosis
What is Essential Thrombocythosis / Essential Thrombocythaemia (ET)?
ET is a condition affecting the bone marrow which causes too many cells called platelets to be produced. Platelets are small cells that circulate around in the blood stream and are involving in blood clotting. The number of platelets that circulate around the body changes a bit but a normal level around is 150 – 400 million for every milliliter of blood. How are platelets normally produced?Platelets are normally produced by cells in the bone marrow called megakaryocytes. ET occurs when the megakaryocytes produce too many platelets and release them into the blood stream. Why does ET occur?It is not fully understood how ET happens but almost definitely involves a change in the genes that control the growth of the megakaryocytes. These gene changes happen spontaneously later in life. A particular gene change that has been identified in a number of people with ET is called the JAK2 mutation. This gene change causes higher levels of a protein in the blood called Thrombopoietin (TPO). TPO ultimately controls the number of platelets that circulate in the blood stream. How common is ET?ET is not common but the true incidence of ET is not known; one study suggests ET occurs in 1 in every 50 000 people. What does having ET mean for me?ET is a serious condition; generally however most people with ET do not have any major symptoms. The two main problem associated with ET are. - Increased risk of clots (thrombosis)
- Increased risk of bleeding
The risk of having a clot or having problems with bleeding depends on a lot of factors – if you have had a clot in the past you may be at a higher risk; if you are older than 60 years of age, your risk may also be greater. You may need to start treatment to reduce the risk of having a blood clot The risk of having problems with bleeding usually only occurs if your platelet count is very high; greater than 1500 million per ml. Are there any other problems with ET I need to worry about?ET can also be associated with other changes occurring in the bone marrow – having ET can be associated with the bone marrow becoming more fibrotic (also called myelofibrosis). Finally, there is also a small chance that the bone marrow changes can lead to leukaemia; this is fortunately quite rare.
What should I do now?
Because an increase in clots (and bleeding) is the most common problem associated with ET, it is very important to reduce the risk of having a blood clot as much as possible. Other risks such as high blood pressure, smoking and having high cholesterol should all be addressed. Regular exercise to maintain a healthy weight is also important. Are there any tablets I can take?Aspirin is a medication that is often used in patients with ET. Aspirin works by interfering with the normal function of platelets. Stopping the platelets from working has been shown to decrease the risk of clots. However, sometimes aspirin can cause an increase in bleeding; you should talk to your doctor about these risks. Resources used to produce this information sheet. - Harrison CN, Green, AR. Essential Thrombocythaemia. Best Practice and Research in Clinical Haematology. Vol 19. No3. pp 439 – 453. 2006
Vannucchi AM, Barbui, T. Thrombocytosis and Thrombosis. Haematology 2007 pp 363 - 370
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