Essential thrombocythemia (ET) is a condition in which the bone marrow produces too many platelets. Platelets are a part of the blood that aids in blood clotting.
Primary thrombocythemia; Essential thrombocytosis
ET results from an overproduction of platelets. As these platelets do not work normally, blood clots and bleeding are common problems. Untreated, ET worsens over time.
ET is part of a group of conditions known as myeloproliferative disorders. Others include:
Many people with ET have a mutation of a gene (JAK2, CALR, or MPL).
ET is most common in middle aged people. It can also be seen in younger people, especially women under age 40.
Symptoms of blood clots may include any of the following:
If bleeding is a problem, symptoms may include any of the following:
If you have life-threatening complications, you may have a treatment called platelet pheresis. It quickly reduces platelets in the blood.
Long-term, medicines are used to decrease the platelet count to avoid complications. The most common medicines used include hydroxyurea, interferon-alpha, or anagrelide. In some people with a JAK2 mutation, specific inhibitors of the JAK2 protein may be used.
In people who are at a high risk of clotting, aspirin at a low dose (81 to 100 mg per day) may decrease clotting episodes.
Many people do not need any treatment, but they must be followed closely by their provider.
Outcomes may vary. Most people can go for long periods without complications and have a normal lifespan. In a small number of people, complications from bleeding and blood clots can cause serious problems.
In rare cases, the disease can change into acute leukemia or myelofibrosis.
Complications may include:
Call your provider if:
Mascarenhas J, Iancu-Rubin C, Kremyanskaya M, Najfeld V, Hoffman R. Essential thrombocythemia. In: Hoffman R, Benz EJ, Silberstein LE, et al, eds. Hematology: Basic Principles and Practice. 7th ed. Philadelphia, PA: Elsevier; 2018:chap 69.
Tefferi A. Polycythemia vera, essential thrombocythemia, and primary myelofibrosis. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 166.