JAK2 and acquired polycythemia vera: Ruxolitinib (Jakafi®, Incyte Corp.), a JAK1/JAK2 inhibitor, has been important in management of myeloproliferative neoplasms, such as myelofibrosis and polycythemia vera, in which gain-of-function mutations in JAK2 are found in 50–95% of patients [7].