Thrombocytosis - Definition

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Thrombocytosis, or thrombocythemia, defines an increase in the number of blood platelets. It is revealed by routine blood count. These platelets are elements of the blood involved in coagulation processes and contribute to primary hemostasis, responsible for forming a thrombus, or blood clot, which stops bleeding. Normal blood platelet count fluctuates between 150,000 and 450,000 per millimeter cubed of blood. If above 450,000, it is called thrombocytosis, carrying the major risk of possible blood clot formation that could block the blood vessels. Thrombocytosis can be caused by conditions of the bone marrow, where platelets are created, in which case it is qualified as primary. It can also be secondary to other conditions, such as cancer, inflammatory disease, or diseases of the spleen, among others. The risks of blood clots only appear to be increased in cases of primary thrombocytosis.