Essential thrombocythemia is an uncommon disorder in which your body produces too many blood platelets. This condition may cause you to feel fatigued, lightheaded and to experience headaches and vision changes. It also increases your risk of blood clots.

Essential thrombocythemia (throm-boe-sie-THEE-me-uh) is more common in people over age 50 and slightly more common in women. Young people can develop it as well.

Essential thrombocythemia is a chronic disease that has no cure. If you have a mild form of the disease, you may not need treatment. If you have a severe condition, you may need  medicine that lowers your platelet count, blood thinners or both.

The first indication you have the disorder may be the development of a blood clot (thrombus). Clots can develop anywhere in your body, but with essential thrombocythemia they occur most often in your brain, hands and feet.

Signs and symptoms depend on where the clot forms. They include:

  • Headache
  • Dizziness or lightheadedness
  • Chest pain
  • Weakness
  • Fainting
  • Temporary vision changes
  • Numbness or tingling of the hands and feet
  • Redness, throbbing and burning pain in the hands and feet (erythromelalgia)
  • Mildly enlarged spleen

Less commonly, essential thrombocythemia may cause bleeding, especially if your platelet count is extremely high (more than 1 million platelets per microliter of blood). Bleeding may take the form of:

  • Nosebleeds
  • Bruising
  • Bleeding from your mouth or gums
  • Bloody stool

If a blood clot occurs in the arteries that supply the brain, it may cause a transient ischemic attack (TIA) or stroke. A TIA, or ministroke, is a temporary interruption of blood flow to part of the brain. Signs and symptoms of a stroke or TIA develop suddenly and include:

  • Weakness or numbness of your face, arm or leg, usually on one side of your body
  • Difficulty speaking or understanding speech (aphasia)
  • Blurred, double or decreased vision

When to see a doctor

Seek medical attention immediately:

  • If you develop signs or symptoms of a TIA or stroke, such as numbness or paralysis on one side of your body
  • If you have any signs or symptoms of abnormal blood clotting or bleeding

Bone marrow — spongy tissue inside your bones — contains stem cells that can become red blood cells, white blood cells or platelets (thrombocytes). Platelets stick together, helping blood to form a clot that stops bleeding when you damage a blood vessel, such as when you get a cut. A normal platelet count ranges from 150,000 to 450,000 platelets per microliter of blood.

If you have essential, or primary, thrombocythemia, your bone marrow makes too many platelet-forming cells (megakaryocytes). The excess platelets may not function normally, leading to abnormal clotting or bleeding.

The exact cause of essential thrombocythemia and similar conditions, known as myeloproliferative disorders, isn't known. About 80 percent of people with the disorder have an acquired gene mutation contributing to the disease. This may involve the Janus kinase 2 (JAK2), calreticulin (CALR) or MPL gene mutation.

A high platelet count that's caused by an underlying condition such as an infection or iron deficiency is called reactive, or secondary, thrombocythemia. People with secondary thrombocythemia have less risk of blood clots and bleeding than do people with essential thrombocythemia.

People with essential thrombocythemia who are older are at risk of complications, as are people who've had prior blood clots or bleeding problems related to the disease.

The abnormal blood clotting of essential thrombocythemia can lead to a variety of potentially serious complications, including:

  • Pregnancy complications. While many women who have thrombocythemia have normal, healthy pregnancies, uncontrolled thrombocythemia can lead to miscarriage and other complications. Your risk of complications may be reduced with regular checkups and medication, so be sure to have your doctor regularly monitor your condition.
  • Stroke. A clot that blocks blood flow to your brain can cause a stroke. If you develop signs and symptoms of a stroke, get immediate medical attention.
  • Heart attack. A clot that obstructs blood flow to your heart can cause a heart attack. Get immediate attention if you develop signs and symptoms of a heart attack. These include pressure, fullness or a squeezing pain in the center of your chest lasting more than a few minutes; pain extending to your shoulder, arm, back, teeth or jaw; shortness of breath; and sweating or clammy skin.

Essential thrombocythemia can also cause bleeding with significant blood loss. A small number of people with essential thrombocythemia may later progress to these potentially life-threatening diseases:

  • Acute myelogenous leukemia. This is a type of white blood cell and bone marrow cancer that progresses rapidly.
  • Myelofibrosis. This progressive bone marrow disorder results in bone marrow scarring, leading to severe anemia and enlargement of your liver and spleen.

Here's some information to help you get ready for your appointment and to know what to expect from your doctor.

What you can do

  • Be aware of any pre-appointment restrictions. At the time you make the appointment, ask if there's anything you need to do in advance, such as restrict your diet.
  • List any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
  • List key elements of your health history, such as blood clots, bleeding incidents and a family history of high platelet counts.
  • List key personal information, including any major stresses or recent life changes.
  • Make a list of all medications, vitamins and supplements that you're taking. Some medications, such as oral contraceptives, can increase the risk of blood clots in women with essential thrombocythemia.
  • Take a family member or friend along. Sometimes it can be difficult to take in all the information you hear during an appointment. Someone who accompanies you may remember something that you missed or forgot.
  • List questions to ask your doctor.

For essential thrombocythemia, some basic questions to ask your doctor include:

  • What kinds of tests do I need?
  • Is my condition temporary or chronic?
  • What treatment  do you recommend?
  • Will I need to take medication?
  • Will I have any side effects from the treatment?
  • What kind of follow up will I need?
  • Do I need to restrict my activity?
  • What are possible complications of my condition?
  • I have other health conditions. How can I best manage them together?
  • Should I see a specialist?
  • Do you have any brochures or other printed material that I can take with me?
  • What websites do you recommend?

Don't hesitate to ask other questions that occur to you during your appointment.

What to expect from your doctor

Your doctor is likely to ask you a number of questions, such as:

  • What signs and symptoms have you noticed?
  • When did you first notice these signs and symptoms?
  • Have they gotten worse over time?
  • Have you had a recent medical procedure or blood transfusion?
  • Have you had a recent infection or vaccine?
  • Do you drink alcohol?
  • Do you have headaches, dizziness or weakness?
  • Do you have any chest pain?
  • Have you had any vision problems?
  • Have you had any bleeding or bruising?
  • Have you experienced any numbness or tingling in your hands or feet?
  • Have you experienced any redness, throbbing or burning pain in your hands or feet?
  • Do you have a family history of high platelet counts?

If your blood count is above 450,000 platelets per microliter of blood, your doctor will look for an underlying condition. He or she will rule out all other causes of high platelet counts to confirm a diagnosis of essential thrombocythemia. Blood tests may include:

  • Complete blood count. This test determines the number of platelets in your blood.
  • Blood smear. A small amount of your blood is examined under a microscope to view the size and activity of your platelets.
  • Genetic testing. Special tests can determine whether you have chromosomal abnormalities that can cause a high platelet count and whether you have a JAK2, CALR or MPL gene mutation.
  • Other blood tests. Your doctor may check the level of iron in your blood or test for markers of inflammation.

Your doctor may also suggest two bone marrow tests:

  • Bone marrow aspiration. Your doctor extracts a small amount of your liquid bone marrow through a needle. The sample is examined under a microscope for abnormal cells.
  • Bone marrow biopsy. Your doctor takes a sample of solid bone marrow tissue through a needle. The sample is examined under a microscope to determine whether your bone marrow has a higher than normal number of the large cells that make platelets (megakaryocytes).

Treatment of essential thrombocythemia depends on your risk of blood-clotting or bleeding episodes. If you're younger than 60 and have had no signs or symptoms, you may simply need periodic medical checkups.

Your doctor may prescribe medication if:

  • You're older than 60 and have had previous blood clots or TIAs
  • You have cardiovascular risk factors, such as high cholesterol, high blood pressure and diabetes


Your doctor may suggest one of the following prescription drugs, perhaps along with low-dose aspirin, to reduce your platelet count or clotting risk:

  • Hydroxyurea (Droxia, Hydrea). This drug suppresses bone marrow production of blood cells, including platelets. Its side effects are usually mild. Your doctor will monitor your blood counts and liver function. There's some concern that long-term use may slightly increase the risk of developing acute myelogenous leukemia.
  • Anagrelide (Agrylin). Unlike hydroxyurea, anagrelide isn't associated with an increased risk of leukemia, but it's not considered as effective. Side effects may include fluid retention, heart problems, headaches, dizziness, nausea and diarrhea.
  • Interferon alfa (Intron A) or pegylated interferon alpha 2a (Pegasys). This drug is given by injection. It may be more expensive and cause worse side effects than hydroxyurea or anagrelide does, but it's the best choice for some people. Side effects may include flu-like symptoms, confusion, nausea, depression, diarrhea, seizures, irritability and sleepiness.

Emergency procedure

A medical procedure called platelet pheresis is used only in emergencies, such as after a stroke or other dangerous blood clotting. It temporarily lowers your platelet count. A needle connected to a tube allows your blood to flow into a device that removes platelets, after which your blood is returned to your body.

If you have essential thrombocythemia, your doctor may recommend you regularly take low-dose aspirin. Aspirin makes platelets less sticky and your blood less likely to form clots. It's often used in pregnancy because it has a low risk of causing side effects to the fetus.

Also try to choose healthy lifestyle habits to lower your risk of developing conditions that may contribute to blood clotting. These include diabetes, high blood pressure and high blood cholesterol. Take steps to:

  • Eat healthy foods. Choose a varied diet rich in whole grains, vegetables and fruits and low in saturated fats. Try to avoid trans fats. Learn about portion control to maintain a normal weight.
  • Increase your physical activity. Aim for at least 30 minutes of moderate physical activity a day. Take a brisk daily walk, ride your bike or swim laps.
  • Achieve or maintain normal weight. Being overweight or obese increases the pressure in the veins in your pelvis and legs and is a risk factor for conditions such as high blood pressure.
  • Stop smoking. If you smoke, take steps to try to stop.
  • Expertise and experience. Mayo Clinic has developed a large essential thrombocythemia practice with highly experienced specialists.
  • Team approach. At Mayo Clinic, you will be treated by a multidisciplinary team of specialized experts, collaborating on your care.
  • Care at Mayo Clinic revolves around you. We listen closely to your needs to find the right treatment. We do our own lab tests, which means less waiting for results. And we explain our findings in plain language.
  • Newest technology and research. Mayo Clinic pioneered the development of innovative drugs to treat symptoms of essential thrombocythemia. Mayo leads many international efforts for essential thrombocythemia and similar disorders.

Mayo Clinic works with hundreds of insurance companies and is an in-network provider for millions of people. In most cases, Mayo Clinic doesn't require a physician referral. Some insurers require referrals or may have additional requirements for certain medical care. All appointments are prioritized on the basis of medical need.

At Mayo Clinic's campus in Phoenix/Scottsdale, Arizona, specialists in hematology/oncology and other areas, as needed, treat people with essential thrombocythemia.

For appointments or more information, call the Central Appointment Office at 800-446-2279 (toll-free) 8 a.m. to 5 p.m. Mountain Standard Time, Monday through Friday or complete an online appointment request form.

At Mayo Clinic's campus in Jacksonville, Florida, specialists in hematology/oncology and other areas, as needed, treat people with essential thrombocythemia.

For appointments or more information, call the Central Appointment Office at 904-953-0853 8 a.m. to 5 p.m. Eastern time, Monday through Friday or complete an online appointment request form.

At Mayo Clinic's campus in Rochester, Minnesota, specialists in hematology and other areas, as needed, treat people with essential thrombocythemia.

For appointments or more information, call the Central Appointment Office at 507-538-3270 7 a.m. to 6 p.m. Central time, Monday through Friday or complete an online appointment request form.

Essential thrombocythemia in children is extremely rare. Treatment for children is coordinated by specialists in pediatric hematology/oncology in Minnesota. Children needing hospitalization receive care at Mayo Eugenio Litta Children's Hospital at Mayo Clinic in Minnesota.

For appointments or more information, call the Central Appointment Office at 507-538-3270 7 a.m. to 6 p.m. Central time, Monday through Friday or complete an online appointment request form.

See information on patient services at the three Mayo Clinic locations, including transportation options and lodging.

Mayo Clinic leads many international efforts for essential thrombocythemia and similar disorders, including roles in the national Myeloproliferative Disorders Research Consortium. Mayo Clinic also hosts conferences on myeloproliferative disorders, which include essential thrombocythemia.


See a list of publications by Mayo Clinic doctors on essential thrombocythemia on PubMed, a service of the National Library of Medicine.

June 24, 2015