JAK2 and acquired polycythemia vera: The JAK2 exon 12 mutation is present in 2% of PV patients; the MPL mutation is present in 5% and 10% of patients with non-mutated JAK2 ET and PMF patients, respectively.6 While somatic mutations observed in other genes, such as TET2, ASXL1, DNMT3A, and EZH2, are found in MPNs, they are revealed in patients both with and without JAK2 and MPL mutations and are not specific to these disorders.