Pathogenesis and management of bleeding in essential thrombocythemia and polycythemia vera.

Patients with essential thrombocythemia (ET) and polycythemia vera (PV) have a paradoxical predisposition to bleeding and thrombotic complications that are major causes of morbidity and mortality. Bleeding manifestations are often associated with extreme thrombocytosis that may lead to acquired von Willebrand syndrome (AVWS). Symptomatic AVWS, in this instance, is managed by platelet cytoreductive therapy and, in case of a life-threatening situation, platelet apheresis may be of additional value. Qualitative platelet defects are prevalent in PV and ET but have not been consistently linked to clinical bleeding. However, in vitro and in vivo hemostatic defects in these disorders are either precipitated or exacerbated by the use of aspirin or other nonsteroidal anti-inflammatory drugs. Additional patient management issues are raised during systemic anticoagulation and surgery. This review summarizes putative pathogenetic mechanisms of bleeding and their management in ET and PV.