Essential Thrombocythemia
A bone marrow disorder that produces too many platelets
Quick Facts
- Type: Chronic blood (myeloproliferative) disorder
- Main problem: Overproduction of platelets
- Key risks: Blood clots and, less often, bleeding
- Often found: By chance on a routine blood test
Overview
Essential thrombocythemia (ET) is a chronic condition in which the bone marrow produces too many platelets, the tiny blood cells that help blood clot. It belongs to a group of disorders called myeloproliferative neoplasms, in which the marrow makes an excess of one or more types of blood cell. In ET the extra platelets do not always work normally, which can lead either to unwanted clotting or, paradoxically, to easy bleeding.
Many people with ET have no symptoms and learn they have it only when a routine blood test shows a high platelet count. The condition tends to progress slowly, and with appropriate monitoring and treatment, most people maintain a normal or near-normal life expectancy. The main goal of care is to prevent clotting complications.
Symptoms
A large share of people have no symptoms at diagnosis. When symptoms do occur, they often relate to changes in blood flow or to clots forming in small or large vessels.
- Headaches, dizziness, or lightheadedness
- Burning, throbbing, or redness in the hands and feet (a symptom called erythromelalgia)
- Numbness or tingling in the hands and feet
- Vision changes, such as blurriness or temporary loss
- Easy bruising or, less commonly, nosebleeds and gum bleeding
- An enlarged spleen, which may cause fullness or discomfort in the upper left abdomen
Signs of a serious clot are a medical emergency. Seek urgent care for chest pain, sudden weakness or numbness on one side of the body, trouble speaking, or a painful, swollen leg.
Causes
Essential thrombocythemia is usually caused by an acquired genetic change in the blood-forming stem cells of the bone marrow. These changes are not inherited from a parent in most cases and are not passed to children; they develop during a person's lifetime.
- JAK2 mutation: The most common genetic change found in ET, present in many people with the condition.
- CALR and MPL mutations: Other gene changes that can drive the overproduction of platelets.
These mutations cause the marrow to make platelets in an uncontrolled way. It is important to distinguish ET from reactive (secondary) thrombocytosis, in which platelets rise temporarily in response to infection, inflammation, iron deficiency, or surgery and return to normal once the trigger resolves.
Risk Factors
- Older age, with diagnosis most common in middle age and beyond
- A history of blood clots, which raises the risk of further clotting
- Cardiovascular risk factors such as high blood pressure, diabetes, and smoking
- Presence of the JAK2 mutation, which is linked to higher clotting risk
Diagnosis
ET is often suspected after a complete blood count shows a persistently high platelet level. Because other conditions can also raise platelets, doctors take steps to confirm the diagnosis and rule out reactive causes.
- Complete blood count (CBC): Repeated over time to confirm a sustained high platelet count.
- Blood smear: Examined under a microscope to look at the size and appearance of platelets and other cells.
- Genetic testing: Blood tests for JAK2, CALR, and MPL mutations.
- Bone marrow biopsy: A sample of marrow that helps confirm ET and distinguish it from related disorders such as early myelofibrosis.
Treatment
Treatment is tailored to a person's risk of clotting and bleeding, based on age, symptoms, platelet count, mutation status, and clotting history. People at low risk may need only monitoring.
- Low-dose aspirin: Often used to lower the risk of clots, unless a person has a high bleeding risk.
- Platelet-lowering medication: Drugs such as hydroxyurea or anagrelide reduce platelet production in people at higher risk.
- Interferon: Sometimes used, including during pregnancy, to control platelet levels.
- Managing other risks: Controlling blood pressure, blood sugar, and cholesterol, and stopping smoking, all lower overall clotting risk.
Care is usually coordinated by a hematologist, with regular blood tests to track the platelet count and adjust treatment over time.
Prevention
Essential thrombocythemia itself cannot be prevented, but its complications often can be reduced.
- Take prescribed medication, such as aspirin or platelet-lowering drugs, exactly as directed
- Keep blood pressure, blood sugar, and cholesterol well controlled
- Avoid smoking, which sharply raises clotting risk
- Stay active and well hydrated, and attend regular follow-up blood tests
- Tell any new doctor or surgeon about the diagnosis before procedures
When to See a Doctor
See a doctor if a blood test shows a high platelet count, or if you have unexplained headaches, vision changes, burning in the hands or feet, or easy bruising. Seek emergency care immediately for signs of a serious clot or bleed, including:
- Chest pain or shortness of breath
- Sudden weakness, numbness, or drooping on one side of the body, or trouble speaking
- A painful, swollen, or red leg
- Severe or uncontrolled bleeding
Frequently Asked Questions
Is essential thrombocythemia a type of cancer?
It is classified as a myeloproliferative neoplasm, a slow-growing blood disorder related to the cancers but generally not aggressive. Most people live a normal or near-normal lifespan with monitoring and treatment. The main concern is preventing blood clots rather than tumor growth.
Can essential thrombocythemia cause both clotting and bleeding?
Yes. The excess platelets often work poorly, so ET can raise the risk of clots in some situations and of easy bleeding in others, especially when platelet counts are very high. This is why treatment is carefully balanced and tailored to each person.
Is essential thrombocythemia inherited?
In most cases the gene changes that cause ET, such as the JAK2, CALR, or MPL mutations, are acquired during life and are not passed to children. A small number of families have an inherited tendency, but this is uncommon. Genetic counseling can help if there is a strong family history.
Do I need treatment if I have no symptoms?
Not always. People at low risk of clotting may simply be monitored with regular blood tests, sometimes with low-dose aspirin. Those at higher risk, such as older adults or people with a clotting history, are usually offered platelet-lowering medication. Your hematologist decides based on your overall risk.
When should I seek emergency care with ET?
Call emergency services for chest pain, sudden one-sided weakness or numbness, trouble speaking, or a painful swollen leg, as these can signal a serious clot. Also seek urgent care for heavy or uncontrolled bleeding. Prompt treatment can prevent lasting harm.
References
- National Heart, Lung, and Blood Institute (NHLBI). Thrombocythemia and Thrombocytosis.
- Mayo Clinic. Essential thrombocythemia.
- MedlinePlus, U.S. National Library of Medicine. Essential thrombocythemia.
- Leukemia & Lymphoma Society. Myeloproliferative Neoplasms.