Table of Contents
Definition of Polycythemia Vera
A myeloproliferative condition of the blood in which the red bone marrow produces an excessive volume of erythrocytes (red blood cells), platelets, and neutrophils that results in increased cell volume and decreased fluid volume (plasma) in the blood.
This myeloproliferation (overproduction by the bone marrow) thickens the blood (hyperviscosity), making it more difficult for the cardiovascular system to transport and increasing the risk for thrombosis (blood clots).
As the myeloproliferation progresses, the marrow pushes immature, deformed, and defective cells into the blood that are unable to perform the normal functions of their cell types.
Polycythemia vera is a chronic and potentially debilitating disorder most commonly diagnosed in people age 60 and older.
Symptoms and Diagnostic Path
Symptoms may not appear until the bone marrow dysfunction is considerably advanced and typically include
- Tiredness and fatigue
- Easy bleeding or bruising
- Pruritus (itching)
- Skin flushing (redness), particularly of the face
The doctor’s examination often reveals an enlarged spleen (splenomegaly), a consequence of the overload on the spleen to remove defective erythrocytes from the circulating blood or to produce additional erythrocytes if those in circulation are too defective to adequately transport oxygen (anemia). Some people also have an enlarged liver (hepatomegaly), as the liver too has a role in cleansing dysfunctional erythrocytes from the blood.
Diagnostic blood tests characteristically show elevated erythrocyte, neutrophil, and platelet counts, with the hematocrit (percentage of erythrocytes in the blood) greater than 54 percent in men or 49 percent in women. The doctor may also perform a bone marrow biopsy, which demonstrates clusters of megakaryocytes (the parent cells of platelets) and other characteristic alterations in the marrow’s structure.
Treatment Options and Outlook
Phlebotomy (therapeutic withdrawal of blood) is adequate treatment for many people who have polycythemia vera, particularly when the diagnosis comes early in the condition. The usual therapeutic approach is daily phlebotomy to remove 300 to 500 milliliters of blood until the hematocrit drops to 45 percent. Weekly to monthly phlebotomy sessions then may keep the condition in check.
When phlebotomy is not sufficient, substances to suppress bone marrow function, called myelosuppressive therapy, can put the condition in remission for up to several years at a time. Myelosuppressive therapy has a high risk for causing acute myeloid leukemia, however, so current treatment protocols call for its use only in people over age 70.
The most significant and frequent complications of polycythemia vera are thrombosis (the formation of blood clots in the blood vessels), which can lead to heart attack or stroke, and acute myeloid leukemia. Without treatment polycythemia vera is generally fatal within two years.
With treatment, many people enjoy good quality of life for 15 to 20 years beyond diagnosis.
Risk Factors and Preventive Measures
Because researchers do not know what causes polycythemia vera, there are no known preventive measures. The condition is uncommon, and more likely to occur in men than women. Polycythemia vera is unusual in a person under age 40. Early diagnosis and treatment improves quality of life and outlook.