Polycythemia vera is a blood cancer that causes red blood cells to multiply. White blood cells and platelets may also multiply.
Polycythemia vera causes the red blood cells to multiply. Red blood cells are the oxygen-carrying cells of the body. Other cells of the blood can also multiply. White blood cells, the infection fighting cells in the body, and platelets, which help blood to clot, are also usually affected.
The cause of polycythemia vera is unknown. It is slightly more common in those who are Jewish. Men are more commonly affected than women. More than 95% of cases occur in people older than 40 years of age.