The reported prevalence of the JAK2 mutation has ranged from 65%-97% in polycythemia vera (PV) patients from Europe and North America, 23%-57% in patients with essential thrombocythemia (ET), and 35%-57% in primary myelofibrosis (PMF) patients (Yonal et al., 2012). The gene discussed is JAK2; the disease is acquired polycythemia vera.