JAK2 and acquired polycythemia vera: Diagnosis of PV is currently according to World Health Organization criteria and based on a composite assessment of clinical and laboratory features, including two major criteria (increased hemoglobin levels and presence of JAK2 mutation) and three minor criteria (trilineage myeloproliferation in bone marrow biopsy, increased serum erythropoietin levels and endogenous erythroid colony formation in vitro) (8).