polycythemia vera

polycythemia vera A disorder of the bone marrow that leads to overproduction of all three blood cell lines: white blood cells, red blood cells, and platelets. Its cause is unknown. Abbreviated PV. PV progresses slowly but may evolve into acute leukemia or myelofibrosis, in which the marrow is replaced by scar tissue. For a diagnosis of PV, there must be polycythemia. See also polycythemia.