The allele burden of JAK2 V617F is related to the clinicohaematological phenotypes of patients with ET, such as older age (p = 0.03), organomegaly (p = 0.003), higher neutrophil count (p = 0.02), thrombotic events (p = 0.01), and myelofibrosis (p = 0.02) in ET, but a larger scale of studies is needed for patients with PV and PMF [28,45]. The gene discussed is JAK2; the disease is acquired polycythemia vera.