If the patient has primary thrombocytosis (for example, essential thrombocythemia), they are at higher risk of thrombosis (though the risk does not correlate well with the platelet count). In patients with secondary or reactive thrombocytosis, there is no compelling evidence supporting an increased risk of thrombosis. Indeed, if anything, they may be at increased risk for bleeding owing to acquired von Willebrand syndrome (though this is far less common in secondary compared with primary thrombocytosis).