The main types of MPNs are chronic myeloid leukemia (CML), characterized by the presence of the Philadelphia chromosome, and the JAK2/CALR/MPL mutation-related MPNs group, also called Philadelphia chromosome negative, including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF)4. The gene discussed is JAK2; the disease is acquired polycythemia vera.