Many people with essential thrombocythemia have no signs or symptoms. The first indication you have the disorder may be the development of a blood clot (thrombus). Although clots can develop anywhere in your body, with essential thrombocythemia, they occur most often in your brain, hands and feet.
Signs and symptoms depend on where the clot forms. They include:
- Dizziness or lightheadedness
- Chest pain
- 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:
- Bleeding from your mouth or gums
- Bloody stool
A blood clot may cause a transient ischemic attack (TIA) — a temporary interruption of blood flow to part of the brain — or stroke. Signs and symptoms 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
If you have any signs or symptoms of abnormal blood clotting or bleeding, see your doctor.
If you develop signs or symptoms of a TIA or stroke, such as numbness or paralysis on one side of your body, seek medical attention immediately.
Bone marrow — spongy tissue inside your bones — contains stem cells that can become red blood cells, white blood cells or platelets. Platelets travel through your blood vessels. They stick together to form clots that stop the 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 thrombocythemia, your bone marrow makes too many platelet-forming cells (megakaryocytes), which release too many platelets into your blood. 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 neoplasms, isn't known. About half the people with the disorder have a mutation of the Janus kinase 2 (JAK2) gene. Other gene mutations also have been linked to essential thrombocythemia.
A high platelet count that's caused by an underlying condition such as an infection or iron deficiency is called reactive or secondary thrombocytosis.
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, be sure to have your doctor regularly monitor your condition. Uncontrolled thrombocythemia can cause miscarriage, premature delivery, high blood pressure (preeclampsia), early separation of the placenta from the uterine wall (placental abruption) and slow fetal growth. Your risk of complications may be reduced with regular checkups and medication.
- 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. If you develop signs and symptoms of a heart attack, such as 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, get immediate medical attention.
Essential thrombocythemia can also cause bleeding (hemorrhage) with significant blood loss. A small minority of people with essential thrombocythemia may later develop acute leukemia or myelofibrosis, both of which can be life-threatening:
- Acute leukemia. Acute myelogenous leukemia is a type of blood and bone marrow cancer that progresses rapidly.
- Myelofibrosis. This progressive bone marrow disorder results in bone marrow scarring, severe anemia, and enlargement of your liver and spleen.