Polycythemia vera (PCV) In this condition, the body makes too many red blood cells, leading to a “thickening” of the blood. It can be associated with an elevated platelet count, and an enlarged spleen.
This slow-developing disease is linked to a mutation in the gene (JAK2) that regulates the production of blood cells. This is an acquired, not an inherited genetic problem, occurring later in life.
PCV is both chronic and progressive. No one knows its cause.