Differential diagnosis of thrombocytosis. Thrombocytosis may be classified according to whether it is primary or secondary. In primary thrombocytosis, the defect is intrinsic to hematopoietic and/or megakaryocytic progenitors. Secondary thrombocytosis is caused by diseases or conditions that result in persistent growth factor-mediated stimulation of otherwise normal megakaryocytopoiesis.
