Myeloproliferative disorder characterized by abnormal proliferation of all hematopoietic bone marrow elements and an absolute increase in red cell mass and total blood volume; associated frequently with splenomegaly, leukocytosis, and thrombocythemia.

In oncology, polycythemia vera (PV) is an uncommon myeloproliferative neoplasm in which the bone marrow makes too many red blood cells. The majority of cases are caused by mutations in the JAK2 gene, most commonly resulting in a single amino acid change in its protein product from valine to phenylalanine at position 617. Most of the health concerns associated with polycythemia vera are caused by the blood being thicker as a result of the increased red blood cells...