An Overview of Polycythemia Vera

Polycythemia vera is a disorder in which the bone marrow makes too many red blood cells, white blood cells, and platelets, which can lead to an increased risk of blood clots.

Having too many red blood cells is the most prominent clinical sign of polycythemia vera. A mutation in a gene for JAK2, a protein involved in signaling within the cell, has been found in many people with this condition.

Illustration of red blood cells

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Who Gets Polycythemia Vera?

Polycythemia vera can occur at any age but often happens later in life. If you look at the ages of all the people with this condition, the middle number for age at diagnosis would be 60 years, and it is not often seen in people under age 40.

How Many People Are Affected?

Polycythemia is diagnosed in 44 to 57 per 100,000 individuals in the U.S., affecting men more than women without a known cause.

According to Incyte Corporation, a Wilmington, Delaware, based biopharmaceutical company specializing in oncology, there are approximately 25,000 people in the United States who live with polycythemia vera and are considered uncontrolled because they develop resistance to or intolerance to a mainstay of drug therapy, hydroxyurea.

Is It a Cancer or a Disease?

Polycythemia vera also falls under a related group of blood cancers called myeloproliferative neoplasms (MPNs). An MPN is an abnormal clone of cells in the bone marrow that, in the case of polycythemia vera, leads to an overproduction of red blood cells. Over time, there is a risk that polycythemia vera can transform into a leukemia. Learning that you or a loved one has this disorder can understandably be stressful. However, know that this condition can be managed effectively for very long periods.

The National Cancer Institute defines polycythemia vera as follows: “A disease in which there are too many red blood cells in the bone marrow and blood, causing the blood to thicken. The number of white blood cells and platelets may also increase. The extra blood cells may collect in the spleen and cause it to become enlarged. They may also cause bleeding problems and make clots form in blood vessels.”

According to The Leukemia & Lymphoma Society, people with polycythemia vera are at slightly greater risk than the general population for developing leukemia as a result of the disease and/or certain established drug treatments. Although this is a chronic condition that is not curable, remember that it can usually be managed effectively for a long, long time—and it does not generally shorten life expectancy. Additionally, complications can be treated and prevented with medical supervision.

Progression of Symptoms

Progression risks for polycythemia vera risks are still being researched. Although people may not have symptoms for many years, polycythemia vera can lead to several symptoms and signs, including fatigue, itchiness, night sweats, pain in the bones, fever, and weight loss. About 30% to 40% of people with polycythemia vera have an enlarged spleen. In some individuals, it leads to heart attack or stroke due to clots constricting blood flow to the major organ. The burden of this disease remains under research.


A test called the hematocrit value is used both to diagnose polycythemia vera and to measure a person’s response to therapy. Hematocrit is the proportion of red blood cells in a volume of blood, and it’s usually given as a percent.

In people with polycythemia vera, hematocrit value is usually higher than 50% in men and 44% in women. Other information that can be gleaned from blood tests is also helpful in the diagnosis, including the presence of a mutation—the JAK2 mutation—in blood cells and low erythropoietin (EPO) levels. For patients with a normal EPO value, bone marrow examination is mandatory for diagnostic confirmation.

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According to The Leukemia & Lymphoma Society, phlebotomy, or the removal of blood from a vein, is the usual starting point of treatment for most patients. The process may lower hematocrit levels and result in decreased condition symptoms including headaches, ringing in the ears, and dizziness.

Drug therapy may involve agents that can reduce red cell or platelet concentrations—compounds referred to as myelosuppressive agents. Hydroxyurea is a myelosuppressive agent used for polycythemia, that may be associated with several side effects including skin changes and hair loss, increased risk of infections, loss of appetite, weight gain, sores in the mouth, headache and constipation.

14 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  6. The National Cancer Institute. Polycythemia vera.

  7. Leukimia & Lymphoma Society. Polycythemia Vera Facts.

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  9. CancerConnect. All Symptomatic Polycythemia Vera Patients May Benefit From Treatment.

  10. Accurso V, Santoro M, Raso S, et al. Splenomegaly impacts prognosis in essential thrombocythemia and polycythemia vera: A single center study. Hematology Reports. 2019;11(4). doi. 10.4081/hr.2019.8281.

  11. Leukemia & Lymphoma Society. Diagnosis.

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  14. MedlinePlus. Hydroxyurea.

Tom Iarocci

By Tom Iarocci, MD
Dr. Iarocci is a Pennsylvania-based medical writer with clinical and research experience in hematology and oncology.