The hallmark laboratory criteria for diagnosing PV are an elevated Hb and/or hematocrit (Hct), low serum erythropoietin (EPO), mutated Janus Kinase 2 (JAK2) and a bone marrow biopsy showing hypercellularity for age, trilineage growth (panmyelosis) and pleomorphic, mature megakaryocytes [5]. The gene discussed is EPO; the disease is acquired polycythemia vera.