JAK2 V617F is found in approximately 50% of ET and PMF patients, but JAK2 V617F allele burden is usually higher in PV than ET patients [23, 24] and JAK2 V617F-positive ET patients generally have higher hemoglobin and lower platelet counts as compared to JAK2 V617F-negative ET patients [25, 26]. The gene discussed is JAK2; the disease is acquired polycythemia vera.