Aspirin for the control of platelet activation and prevention of thrombosis in essential thrombocythemia and polycythemia vera: current insights and rationale for future studies.

Polycythemia vera and essential thrombocythemia are chronic myeloproliferative disorders characterized by a relatively benign clinical course that may be complicated by arterial and venous thromboses. A thrombotic diathesis often manifests at diagnosis or in the preclinical phase of the myeloproliferative disease. Peculiar microcirculatory disturbances such as erythromelalgia and visual and hearing symptoms also commonly occur in these patients, and are highly responsive to aspirin. In a placebo-controlled trial in relatively low-risk polycythemic subjects, low-dose aspirin recently was shown to reduce the incidence of both arterial and venous thrombosis with a limited increase of the hemorrhagic risk. Due to its favorable benefit/risk profile, low-dose aspirin should be prescribed to all patients with polycythemia vera who have no contraindication to this treatment. Future studies should assess primarily the efficacy and safety of aspirin in essential thrombocythemia, and test the possible use of more aggressive antithrombotic strategies in high-risk polycythemic patients.