Janus Kinase 2 (JAK2) V617F is the most common genetic mutation in these diseases and is found in 95% of patients with PV and 50% – 60% of patients with ET, which results in constitutive kinase activity promoting both hematopoietic cells proliferation and a proinflammatory state (2–5). The gene discussed is JAK2; the disease is acquired polycythemia vera.