Essential Thrombocythemia

Table of Contents

Essential thrombocythemia (ET) is a rare type of blood cancer. It occurs when the body makes too many platelets, the part of the blood needed for clotting. Researchers are still trying to understand the causes of ET, which is one of 3 myeloproliferative neoplasms (MPNs). There is no cure for ET but people with the disease often live normal lives.

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Risk Factors

The causes of essential thrombocythemia are largely unknown. It occurs more often in people over 50, and slightly more often in women. It is usually not passed down through families. Approximately half of people with this disease have an abnormal change in the JAK2 gene. Other genes such as CALR or MPL may be involved as well. 


Signs & Symptoms

Many people with essential thrombocythemia show minimal signs or symptoms. If signs and symptoms occur, they may include:

  • Headache
  • Throbbing or burning pain in feet or hands
  • Lightheadedness or dizziness
  • Enlarged spleen
  • Thrombosis (abnormal clotting)
  • Bleeding (less common)
  • Fatigue
  • Weakness
  • Sweating



Diagnosis of essential thrombocythemia requires blood testing. A complete blood count measures blood cells and platelets. Normal platelet levels are between 150,000 to 400,000 platelets per microliter (μL) of blood. Consistently elevated platelet levels may be a sign of essential thrombocythemia. Your doctor may order the following tests to gather more information or rule out other causes:

  • Testing for the presence of JAK2 mutation or other genetic mutations (e.g. CALR, MPL)
  • Bone marrow biopsy and aspirate, helps to rule out other causes and confirm an ET diagnosis


Different healthcare providers involved in your care may include a hematologist/oncologist, a nurse, a nurse navigator, an oncology social worker, or a pharmacist. These people can help you find information and resources that may be useful before, during, and after treatment. Ask your doctor about the other members of your healthcare team, their names, and how you can arrange to meet them. You also may want to ask your insurance company to assign you a case manager to help you understand which treatments and services your health insurance will cover.

Treatment choices depend on your diagnosis and the extent of the disease. The various drugs used to treat essential thrombocythemia work in different ways and may have different side effects. Ask for more information before starting treatment. Your options may include:

Aspirin, taken orally, in low doses, can help reduce the risk of clotting and is recommended for most ET patients.

Cytoreductive therapies (e.g. hydroxyurea, anagrelide), which may reduce the blood counts, are usually given by mouth (orally), and are recommended for patients considered high risk for blood counts (i.e. age > 60 or history of a prior blood clot).

Interferon alfa, which can lower blood counts, is given subcutaneously. Sustained release preparations (e.g. peginterferon alfa-2a), have superior tolerability.

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