✅ Thrombocytosis is a platelet count > 450 x 109/L. Extreme thrombocytosis describes a platelet count > 1000 x 109/L.
✅ Thrombocytosis may be primary or secondary.
✅ Primary thrombocytosis may be familial or acquired. The most common acquired form of primary thrombocytosis is essential thrombocythemia.
✅ Secondary thrombocytosis, also called reactive thrombocytosis, is far more common that primary thrombocytosis, constituting about 85% of cases.
✅ Secondary thrombocytosis is caused by myriad conditions including infections, inflammation, iron deficiency, trauma, drugs and post-splenectomy state.
✅ Primary thrombocytosis, but not secondary thrombocytosis, is associated with an increased risk of thrombosis and hemorrhage.
✅ Treatment of primary of thrombocytosis includes antiplatelet agents and cytoreductive therapy.
✅ Treatment of secondary thrombocytosis is to address the underlying cause.