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.

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 why.

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.

Diagnosis

A test called the hematocrit concentration 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 healthy people, hematocrit concentration range based on race and age, with men being between 41%-51% and women from 36%-44%. 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. Although it’s not required to make the diagnosis, some people may also have a bone marrow analysis as part of their workup and evaluation.

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Treatment

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. Though the process may lower hematocrit levels that 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 myelosuppresive agent used for polycythemia, causing several side effects including, loss of appetite weight gain, sores in the mouth and throat, and constipation.