Essential Thrombocythemia

Essential thrombocythemia is a rare genetic disorder that affects platelets, the blood cells that control bleeding. People with this condition develop many blood clots. This increases their risk of heart attack or stroke. Healthcare providers treat this condition by reducing platelet levels, which reduces the risk of serious complications.


What is essential thrombocythemia?

Essential thrombocythemia or primary thrombocythemia (pronounced thräm-bō-sī-thē-mē-ə) is a rare blood disorder that happens when abnormal stem cells in your bone marrow make too many platelets. Platelets are blood cells that slow or stop bleeding by creating blood clots. Essential thrombocythemia is an acquired genetic condition, meaning it happens when certain genes mutate or change.

You may learn you have this condition when a routine blood test shows your platelet levels are unusually high. You may not have symptoms and you may not need immediate treatment. Essential thrombocythemia is not curable but treatment may reduce the risk you’ll develop serious complications.

How does this condition affect my body?

Essential thrombocythemia affects your platelets, the tiny, sticky blood cells that are first on the scene if your blood vessels rupture from injury or disease. Because platelets are sticky, they quickly form clumps that literally plug holes in damaged blood vessels.

Your bone marrow produces platelets along with red and white blood cells. Normally, your bone marrow acts like a factory supervisor, carefully monitoring supply and demand so you have just enough platelets on hand to slow or stop bleeding.

In essential thrombocythemia, however, your bone marrow produces more platelets than your body needs. The abnormal platelets are also larger than normal and oddly shaped. Like excess inventory that takes up space in already-crowded storage areas, the abnormal platelets make blood clots that crowd into blood vessels and block blood flow.

Essential thrombocythemia can cause blood clots anywhere in your body, especially in your brain, hands and feet. People who are pregnant or planning to become pregnant have additional risk of developing blood clots during pregnancy.

This condition may also cause unusual or excessive bleeding. That may sound odd since essential thrombocythemia usually makes your blood clot, or stop flowing. In this situation, unusual or excessive bleeding happens because the dramatic increase in blood clots uses up platelets in your bloodstream, leaving you without platelets to slow or stop bleeding. People with essential thrombocythemia may have increased risk of a heart attack or a stroke.

Is essential thrombocythemia a form of cancer?

Essential thrombocythemia is an example of a myeloproliferative neoplasm. These are blood cancers that happen when your body produces too many blood cells.

Is essential thrombocythemia a form of leukemia?

No, but some people with essential thrombocythemia may develop leukemia.

What’s the difference between essential thrombocythemia and thrombocytosis?

If you have essential thrombocythemia, you have a high platelet count that isn’t related to another medical condition. If you have reactive thrombocytosis, your platelet count is high because you have another disease or condition. Thrombocytosis is more common than thrombocythemia.


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Who is affected by this condition?

Essential thrombocythemia is a rare disease that affects about 2 in 100,000 people in the United States. This condition affects twice as many people assigned female at birth (AFAB) than people assigned male at birth (AMAB).

This condition typically affects people between age 60 and 80. About 20% of all cases involve people age 40 and below. Children rarely have this condition, and when they do, it’s because they inherited it from a biological parent.

Symptoms and Causes

What are essential thrombocythemia symptoms?

Essential thrombocythemia symptoms may vary from person to person. This condition develops over time as your bone marrow produces more platelets and your platelet levels rise. You can have this condition without having any symptoms. As platelet levels rise, you may develop blood clot symptoms. Blood clots from essential thrombocythemia can form anywhere in your body but they typically form in your brain, hands or feet.

Symptoms of blood clots

  • Chronic or long-term headache.
  • Dizziness.
  • Burning or throbbing feeling in the palms of your hands and soles of your feet.
  • Numb or red hands and feet.
  • Changes in your pattern of speech.
  • Migraines.
  • Seizures.
  • Pain or discomfort in your upper body, including your arms, back, neck, jaw or belly (abdomen).
  • Nausea.
  • Feeling short of breath (dyspnea).
  • Chest pain.
  • Weakness.
  • Enlarged spleen.
  • Nosebleeds (epistaxis).
  • Bleeding gums.
  • Blood in your poop (stool).
  • Blood in your pee (urine) or hematuria.
  • Bruising more easily.
  • Heavy menstrual periods.

How does this condition affect pregnancy?

Blood clots are a potential problem any time someone is pregnant. Women and people assigned female at birth with essential thrombocythemia have an increased risk for blood clots. Some common essential thrombocythemia treatments aren’t appropriate for people who are pregnant or planning to be pregnant.

Remember, essential thrombocythemia may cause people to have heart attacks and/or strokes. If you have this condition and think you may be having a heart attack or stroke, call 911 immediately.


What causes essential thrombocythemia?

Essential thrombocythemia is an acquired genetic disorder. You’re not born with these disorders. Instead, they happen when genes inside certain cells mutate or change. In this case, the genes that mutate affect stem cells in your bone marrow that make blood cells. Those genes are JAK2, CALR and MPL:

  • JAK2 stands for Janus kinase 2. The JAK2 gene tells cells how to make the JAK2 protein. This protein helps to control how stem cells produce blood cells.
  • The CALR gene provides instruction on making the calreticulin protein. Researchers believe calreticulin helps to control gene activity, how cells grow and divide and when cells die.
  • MPL stands for myeloproliferative leukemia virus. The MPL gene is an oncogene. Oncogenes are genes that may cause cancer.

When these genes mutate, they set off a chain reaction that puts stem cell production into overdrive, producing more platelets than your body can use.

Diagnosis and Tests

How do healthcare providers diagnose essential thrombocythemia?

Healthcare providers diagnose this condition by doing a physical examination. They may ask about your symptoms and if you have family members with similar problems. They typically order the following tests:

  • Complete blood count (CBC): This test measures all blood cell levels, including platelets.
  • Peripheral blood smear: Abnormal platelets are larger than normal platelets or oddly shaped. In this test, providers examine blood samples under a microscope to look at your platelets and other blood cells.
  • Bone marrow tests: Providers may do bone marrow aspiration or bone marrow biopsy to evaluate your bone marrow.
  • Genetic testing: Providers may analyze your blood, looking for changes in the genes that may affect platelet production.

Test results help providers assess your risk and create treatment plans. In general, the factors that put you at an increased risk of essential thrombocythemia include:

  • Being 60 years and older.
  • Being a woman or a person assigned female a birth.
  • Having a history of blood clots.
  • Carrying the mutated genes that cause essential thrombocythemia.


Management and Treatment

Does essential thrombocythemia require treatment?

That depends on your situation. Some people have this condition but don’t have symptoms. In that case, healthcare providers may recommend watchful waiting. Just as it sounds, watchful waiting means healthcare providers watch over your health, waiting for early indications of essential thrombocythemia symptoms.

What medications/treatments are used?

Healthcare providers may treat essential thrombocythemia with medications that prevent blood clots and/or lower platelet levels. Medications include:

  • Aspirin: Aspirin prevents blood clots. Your provider may recommend you take aspirin to reduce your blood clot risk. People who have extremely high platelet counts should check with their providers before taking aspirin. If you have a very high platelet count, your provider may do tests to make sure you don’t have acquired Von Willebrand syndrome. People with this syndrome have increased risk of excessive bleeding.
  • Hydroxyurea (Droxia®, Hydrea ®, Siklos®, Mylocel®): Hydroxyurea (pronounced hye-drox-ee-ure-ee-a) is a chemotherapy medication that lowers platelet levels. If you have high blood clot risk, your provider may combine aspirin and hydroxyurea.
  • Anagrelide (Agrilyn®): Like hydroxyurea, anagrelide (pronounced an-AH-gre-lide) lowers platelet levels and helps reduce stroke and heart attack risk.
  • Interferon alfa (Multiferon®): Interferon alfa(pronounced In-ter-FEER-on Al-fa) is a form of immunotherapy that keeps abnormal platelets from dividing and multiplying.
  • Busulfan (Busulfex®, Myleran®): Busulfan (pronounced byoo-suhl-fin) is a chemotherapy medication that lowers platelet levels and helps people who can’t take hydroxyurea or don’t benefit from taking hydroxyurea.
  • Ruxolitinib (Jakafi®): Ruxolitinib(pronounced ruhk-sow-li tuh-nuhb) is a medication that helps people who don’t appear to benefit from treatment with hydroxyurea, busulfan and interferon alfa and who have symptoms including itching, feeling full even when they don’t eat much food and have fatigue.

If you have very high platelet levels, your provider may recommend plateletpheresis to lower your platelet levels right away. In plateletpheresis, healthcare providers use a special machine to remove some of your platelets from your bloodstream.


Can I reduce the risk I will develop this condition?

No, you can’t. Essential thrombocythemia is an acquired genetic disorder that happens when certain genes mutate. Researchers don’t know why these genes mutate, so you can’t prevent that from happening.

Outlook / Prognosis

Can you live a normal life with essential thrombocythemia?

Absolutely. Even if you have symptoms, providers can provide treatments to prevent serious complications such as stroke or heart attack.

What is the life expectancy for someone who has essential thrombocythemia?

People with this condition may not live as long as people who don’t have it. Many things affect how long you may live. If you have this condition, talk to your healthcare provider about your prognosis. They know you and your situation and are your best resource for this kind of information.

Living With

How do I take care of myself?

People with essential thrombocythemia have an increased risk of developing blood clots and/or bleeding more than usual. You may reduce that risk by:

  • Not smoking cigarettes: People who smoke are more likely to develop blood clots than those who don’t. If you smoke, ask your healthcare about programs to help you stop.
  • Maintaining a healthy weight: People who have obesity may develop blood clots. If you need help developing healthy eating habits, ask to speak with a nutritionist.
  • Getting some exercise: Exercise reduces blood clot risk.
  • Managing medical conditions that increase blood clot risk: People who have diabetes or high blood pressure may develop blood clots.
  • Keeping track of your overall health: You can have essential thrombocythemia without symptoms. Your provider will be glad to review potential symptoms so you know what to look for.

When should I see my healthcare provider?

You should have regular checkups so your provider can evaluate your overall health and check for essential thrombocythemia symptoms. They may do blood tests to check on platelet levels.

When should I go to the emergency room?

People who have essential thrombocythemia are at risk for heart attack and stroke. If you have the following symptoms, call 911 right away.

Heart attack symptoms

Women and people AFAB may have different symptoms. They’re less likely to have chest pain and/or feeling as they have indigestion. They may have the following symptoms:

Stroke symptoms

  • Suddenly feeling numb.
  • Suddenly weakness that affects one side of your face or arms on one side of your body.
  • Suddenly having trouble speaking.
  • Sudden difficulty seeing with one or both eyes.
  • Severe dizziness or loss of balance, coordination or ability to walk.
  • Sudden severe headache for no reason.

What questions should I ask my healthcare provider?

Essential thrombocythemia is a rare disease. You may wonder why you developed this disease and what you can do about it. Here are some questions you may want to ask your provider:

  • Why do I have this condition?
  • I feel fine now. When will I develop symptoms?
  • What does watching waiting mean?
  • What medications do you recommend?
  • Will I need to take medication for the rest of my life?

A note from Cleveland Clinic

Essential thrombocythemia is a rare genetic disorder that affects your platelets, increasing your risk of developing blood clots, having a heart attack or a stroke. Essential thrombocythemia is an acquired genetic disorder. You don’t inherit this disorder. It happens when something causes certain genes to change or mutate after you’re born. Healthcare providers can’t cure essential thrombocythemia, but they can prevent blood clots with treatments that reduce platelet levels — and your risk of heart attack or stroke.

Medically Reviewed

Last reviewed on 08/17/2022.

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