People who have thrombocythemia or thrombocytosis may not have signs or symptoms. These conditions might be discovered only after routine blood tests.
However, people who have primary thrombocythemia are more likely than those who have secondary thrombocytosis to have serious signs and symptoms.
The signs and symptoms of a high platelet count are linked to blood clots and bleeding. They include weakness, bleeding, headache, dizziness, chest pain, and tingling in the hands and feet.
In primary thrombocythemia, blood clots most often develop in the brain, hands, and feet. But they can develop anywhere in the body, including in the heart and intestines.
Blood clots in the brain may cause symptoms such as chronic (ongoing) headache and dizziness. In extreme cases, stroke may occur.
Blood clots in the tiny blood vessels of the hands and feet leave them numb and red. This may lead to an intense burning and throbbing pain felt mainly on the palms of the hands and the soles of the feet.
Other signs and symptoms of blood clots may include:
- Changes in speech or awareness, ranging from confusion to passing out
- Upper body discomfort in one or both arms, the back, neck, jaw, or abdomen
- Shortness of breath and nausea (feeling sick to your stomach)
In pregnant women, blood clots in the placenta can cause miscarriage or problems with fetal growth and development.
Women who have primary thrombocythemia or secondary thrombocytosis and take birth control pills are at increased risk for blood clots.
If bleeding occurs, it most often affects people who have platelet counts higher than 1 million platelets per microliter of blood. Signs of bleeding include nosebleeds, bruising, bleeding from the mouth or gums, or blood in the stools.
Although bleeding usually is associated with a low platelet count, it also can occur in people who have high platelet counts. Blood clots that develop in thrombocythemia or thrombocytosis may use up your body's platelets. This means that not enough platelets are left in your bloodstream to seal off cuts or breaks on the blood vessel walls.
Another cause of bleeding in people who have very high platelets counts is a condition called von Willebrand Disease. This condition affects the blood clotting process.
In rare cases of primary thrombocythemia, the faulty bone marrow cells will cause a form of leukemia (lu-KE-me-ah). Leukemia is a cancer of the blood cells.