Thrombocytosis

Thrombocytosis (or thrombocythemia) is the presence of high platelet counts in the blood, and can be either primary (also termed essential and caused by a myeloproliferative disease) or reactive (also termed secondary). Although often symptomless (particularly when it is a secondary reaction), it can predispose to thrombosis in some patients. Thrombocytosis can be contrasted with thrombocytopenia, a loss of platelets in the blood.