In polycythemia vera, the blood becomes thickened with too many red blood cells. The number of white blood cells and platelets may also increase. These extra blood cells may collect in the spleen and cause it to swell. The increased number of red blood cells or platelets in the blood can cause bleeding problems and make clots form in blood vessels. This can increase the risk of stroke or heart attack. In patients who are older than 65 years or who have a history of blood clots, the risk of stroke or heart attack is higher. Patients also have an increased risk of developing acute myeloid leukemia or primary myelofibrosis.
Polycythemia vera often does not cause early symptoms. It is sometimes found during a routine blood test. Symptoms may occur as the number of blood cells increases. Other conditions may cause the same symptoms. A doctor should be consulted if any of the following problems occur:
In addition to a complete blood count, bone marrow aspiration and biopsy, and cytogenetic analysis, a serum erythropoietin test is used to diagnose polycythemia vera. In this test, a sample of blood is checked for the level of erythropoietin (a hormone that stimulates new red blood cells to be made).