What Causes Polycythemia Vera?

Polycythemia vera (PV) also is known as primary polycythemia. A mutation, or change, in the body's JAK 2 gene causes PV. The JAK 2 gene makes an important protein that helps the body produce blood cells. What causes the change in the JAK 2 gene isn't known. PV isn't passed from parent to child. However, in some families, there may be a tendency for the JAK 2 gene to mutate.

There is another kind of polycythemia not related to the JAK 2 gene. This is called secondary polycythemia. The cause of secondary polycythemia is known. It is caused by long-term exposure to low levels of oxygen. Long-term lack of oxygen can cause your body to produce more of the hormone erythropoietin (EPO). EPO increases the production of red blood cells above normal levels, leading to thickening of the blood as in PV. People who smoke, spend long hours at high altitudes (such as mountaineers and pilots), or have severe lung or heart disease may develop secondary polycythemia. In some cases, secondary polycythemia can be cured, depending on whether the underlying cause can be controlled or cured.