Anticoagulant-resistant thrombophilia in a patient with polycythemia vera: a case report.

Mechanical valve thrombosis is a rare condition in an adequately anticoagulated patient in the absence of underlying thrombophilia. We report a case of a 76-year-old male with mechanical prosthetic mitral valve thrombosis as the presenting feature of polycythemia vera. The patient was treated with thrombolysis at the time of acute presentation and subsequently maintained on low molecular weight heparin, low-dose aspirin, phlebotomy and hydroxyurea. Hemoglobin, leucocytosis and platelet count were controlled for almost 4 years after which the patient suffered a second, fatal episode in the setting of therapeutic anti-Xa level. This case report highlights the thrombotic risks associated with polycythemia vera. The proposed mechanisms of hypercoagulability in polycythemia vera are reviewed. To the best of our knowledge, mechanical valve thromboses as the presenting feature of polycythemia vera has not been reported previously.