What Are Thrombocythemia and Thrombocytosis?
Thrombocythemia (THROM-bo-si-THE-me-ah) and thrombocytosis (THROM-bo-si-TO-sis) are conditions in which your blood has a high number of blood cell fragments called platelets (PLATE-lets). Platelets are made in your bone marrow along with other kinds of blood cells. They travel through your blood vessels and stick together (clot) to stop any bleeding that could happen if a blood vessel is damaged. Platelets also are called thrombocytes (THROM-bo-sites), because a clot also is called a thrombus. A normal platelet count ranges from 150,000 to 450,000 platelets per microliter of blood.