Thrombosis in myeloproliferative disorders: pathogenetic facts and speculation

The thrombophilic state of patients with myeloproliferative disorders (MPD) is associated with complex and peculiar hemostatic abnormalities which have been extensively investigated over the last three decades. Research efforts were mainly aimed at elucidating the pathogenesis of thrombophilia, at identifying biological markers of vascular risk as well as at developing rational and safe antithrombotic strategies. These objectives are still partially unmet. Laboratory studies have provided a relevant amount of data which, however, were often conflicting or difficult to interpret as to their clinical or pathogenetic significance. Organizing these pieces of knowledge in mechanistic hypotheses might be difficult without the clues provided by clinical studies which, over the last five years, added new information on clinical epidemiology and treatment of patients with Polycythemia Vera (PV) and Essential Thrombocythemia (ET). Thus, in this paper the results of laboratory studies will be discussed together with some clinical data gathered in these diseases in which also hemostatic abnormalities have been most extensively investigated. Clinical and laboratory data on other myeloproliferative disorders are scant and will not be discussed in this paper.