Causes

Polycythemia vera occurs when a mutation in a gene causes a problem with blood cell production. Normally, your body regulates the number of each of the three types of blood cells you have — red blood cells, white blood cells and platelets. But in polycythemia vera, your bone marrow makes too many of some of these blood cells.

The cause of the gene mutation in polycythemia vera is unknown, but it's generally not inherited from your parents.