JAK2 and acquired polycythemia vera: In PV, on the other hand, the gain-of-function mutation in the JAK2 gene (JAK2 V617F) constitutively activates type-1 myeloid cytokine receptor-mediated signaling [3,4,5,6,36], resulting in myeloproliferation and systemic inflammation with a protracted clinical course and near-normal life expectancy [37].