Causes of secondary thrombocytosis:
(1) acute inflammatory response (due to infection, autoimmune disease, etc)
(2) non-hematologic malignancy
(3) post-splenectomy or with hyposplenism
(4) hemorrhage
(5) iron deficiency anemia
(6) following a surgical procedure
(7) following trauma
(8) rebound proliferation following chemotherapy
(9) rebound proliferation following therapy for vitamin B12 or folate deficiency
General features suggesting a secondary thrombocytosis:
(1) identifiable cause
(2) either transient or reverses after underlying cause is treated
(3) associated with elevation of acute phase reactants
(4) not associated with hypercoagulability (exceptions may be non-hematologic malignancy and bedrest after trauma or surgery)
The diagnosis of thrombocytosis can be challenging if both primary and secondary thrombocytosis are present.
