Why does my patient have erythrocytosis?

Primary polycythemias are the result of intrinsic abnormalities of the hematopoietic progenitors that lead to constitutive overproduction of red cells accompanied by low erythropoietin (EPO) levels. Secondary polycythemias are caused by conditions resulting in increased EPO production. Polycythemia vera (PV) is a primary polycythemia, and is a chronic clonal progressive myeloproliferative neoplasm. A single recurrent point mutation in the pseudokinase domain of JAK2 molecule (JAK2(V617F)) is present in >95% of patients with PV. The goal of therapy in PV is to normalize blood counts to minimize the risk of thrombotic events.