Polycythemia vera (PV) is a type of blood cancer that causes the bone marrow to make too many red blood cells. These cells carry oxygen throughout the body, but when too many of them, the blood becomes thicker and can cause circulation problems, such as blood clots. PV is a rare, slow-onset disease that usually affects people over 50.
PV is a rare disease that affects about 2 or 3 people in every 100,000 inhabitants. PV affects men more than women and is more common in people of Jewish descent.