The Philadelphia chromosome-negative chronic myeloproliferative neoplasms (MPNs) are a group of hematopoietic stem cell malignancies that include polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). PV and ET can evolve into myelofibrosis, termed post PV/ET MF. ET, PV and PMF have variable tendencies to transform to blast phase disease with a dismal prognosis. JAK2V617F is a point activating mutation resulting in the constitutive activity of the JAK-STAT pathway within hematopoietic cells in approximately 96%, 50%, and 50% of patients with PV, ET, and MF, respectively.