ABSTRACT
The Philadelphia-negative myeloproliferative disorders (MPD) are clonal hematological malignancies with three main members: polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). 1 They are thought to result from transformation of a multipotent stem cell 2,3 and are characterized by overactive hematopoiesis, with increased red cell mass and platelets being the defining features of PV and ET, respectively. The major complications are thrombosis, either arterial or venous, and hemorrhage, with a long-term risk of myelofibrotic or acute leukemic progression. 4
This chapter focuses primarily on ET, although many of the recent advances in our understanding of the molecular biology, diagnosis, and management of these conditions apply across all the MPD. William Dameshek was the first to link the MPD as a spectrum of related diseases in 1951, 5 together with chronic myeloid leukemia (CML), recognizing the significant overlap in clinical and laboratory features, such as marrow hypercellularity, propensity to thrombosis and hemorrhage, and risk of leukemic or myelofibrotic transformation over time.
