 The myeloproliferative neoplasms MPN, most notably polycythemia vera PV, essential thrombocythemia ET, and primary myelofibrosis PMF are a diverse but inter-related suite of clonal disorders of pluripotent hematopoietic stem cells Tefferi et al., 2008. The MPN share a range of biological, pathological, and clinical features including the relative overproduction of one or more cells of myeloid origin, growth factor independent colony formation in vitro, marrow hypercellularity, extramedullary hematopoiesis, splenomegaly and hepatomegaly, and thrombotic andor hemorrhagic diatheses Tefferi et al., 2005. 