thrombocytosis /throm′bōsītō″sis/ [Gk, thrombos + kytos + osis, condition] , an abnormal increase in the number of platelets in the blood. Benign thrombocytosis, or secondary thrombocytosis, is asymptomatic and usually occurs after splenectomy, inflammatory disease, hemolytic anemia, hemorrhage, or iron deficiency; as a response to exercise; after chemotherapy; in chronic myelogeneous leukemia; or in advanced carcinoma, Hodgkin’s disease, or other lymphomas. Essential thrombocythemia is characterized by episodes of spontaneous bleeding alternating with thrombotic episodes. The platelets may reach levels exceeding 1,000,000/μL. Compare thrombocytopenia. See also polycythemia.
