Polycythemia vera is a myeloproliferative neoplasm of the blood-producing cells of the bone marrow that results in overproduction of all types of blood cells. Polycythemia vera is due to mutations in the Janus kinase 2 (JAK2) gene, which produces a protein (enzyme) that stimulates excessive production of blood cells. People may feel tired and weak, light-headed, or short of breath, or develop symptoms caused by blood clots. Blood tests are done for diagnosis. Phlebotomy is done to remove excess red blood cells, and some people take aspirin and sometimes other drugs.
In polycythemia vera, the excess of red blood cells increases the volume of blood and makes it thicker, so that it flows less easily through small blood vessels.
Polycythemia vera occurs in about 2 in every 100,000 people. The average age at which the disorder is diagnosed is 60, but it also occurs in people younger than 40. More men than women develop polycythemia vera over age 60, but more women than men develop the disease under age 40.
More than 95% of people with polycythemia vera have a mutation in the JAK2 gene. This mutation causes excess blood cell production.
In addition, mutations in the calreticulin gene (CALR) and other genes have been found in some people with polycythemia vera. These mutations lead to sustained activation of JAK2 kinase, the enzyme that causes excess red blood cell production.
Often, people with polycythemia vera have no symptoms for years. The earliest symptoms usually are
Weakness
Tiredness
Headache
Light-headedness
Shortness of breath
Night sweats
Itching after a shower or bath
Vision may be distorted, and people may have blind spots or see flashes of light (ocular migraine).
People may have bleeding from the digestive tract or gums and more bleeding than would be expected from small cuts.
A
blood clot sometimes causes the first symptoms. The increase in red blood cells in polycythemia vera makes the blood thicker and more likely to clot more than normal. A clot may form in almost any blood vessel, including those of the arms, legs (causing
deep vein thrombosis
Deep Vein Thrombosis (DVT) Deep vein thrombosis is the formation of blood clots (thrombi) in the deep veins, usually in the legs. Blood clots may form in veins if the vein is injured, a disorder causes the blood to clot... read more
Blood tests
Genetic tests and other tests
Polycythemia vera may be discovered through a blood count done for another reason, even before people have any symptoms. The number of red blood cells, the level of the protein that carries oxygen in red blood cells (hemoglobin) and the percentage of red blood cells in the total blood volume (the hematocrit) are abnormally high. The number of platelets and white blood cells may also be increased.
Blood levels of erythropoietin, a hormone that stimulates the bone marrow to produce red blood cells, also may be measured. Levels of erythropoietin are usually, extremely low in polycythemia vera, and they are often, but not always, normal or high in secondary erythrocytosis.
People are tested for JAK 2 gene mutations to confirm the diagnosis of polycythemia vera. If those mutations are not found, doctors look for CALR and sometimes other mutations, which are also helpful in confirming the diagnosis.
Removing blood (phlebotomy) to reduce the number of red cells
Drugs as needed to decrease the number of platelets, prevent complications, or relieve symptoms
Aspirin can help relieve symptoms related to the high platelet counts, such as migraines that affect vision and burning pain and redness of the hands and feet. However, aspirin has not been proven to decrease the risk of blood clots in polycythemia vera and does not benefit people who do not have symptoms
People who continue to have symptoms after having phlebotomy may need other treatments. For such people, doctors may use ruxolitinib, a drug that inhibits the activity of JAK2 , or other drugs, including pegylated interferon alfa-2b, anagrelide, or hydroxyurea.
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