Thrombocytosis

Thrombocytosis is usually discovered incidentally, but the differential diagnosis is important. In cases of reactive, or secondary, thrombocytosis, the underlying disease may require treatment. Clonal thrombocytosis, in contrast, is associated with both thrombotic and bleeding complications, and cytoreductive treatment may be necessary. This review also summarizes the current understanding of platelet production. Clonal thrombocytosis is associated with both thrombotic and bleeding complications. Thrombocytosis is typically discovered as an incidental laboratory abnormality when the complete blood count is obtained for some unrelated reason. When found, however, it creates an important diagnostic challenge. Thrombocytosis generally either is a reactive process (secondary thrombocytosis) or is caused by a clonal bone marrow (myeloproliferative) disorder; the latter category includes essential thrombocythemia. It is often exceedingly difficult to differentiate between the reactive and clonal types of thrombocytosis on the basis of clinical findings or laboratory test results. Yet there are fundamental differences between them in terms of cause, pathophysiological features, and clinical implications. Mechanisms of Thrombocytosis Thrombopoietin is . . .