Polycythemia vera is a condition characterized by an increased number of red blood cells in the bloodstream. Affected individuals may also have excess white blood cells and blood clotting cells called platelets.

Blood is carried throughout your body by a system of veins and arteries. When there are too many red blood cells in your blood it becomes thicker and flows more slowly. The red blood cells can begin to form clots within the blood vessels. In PV, clots are formed when large amounts of red blood cells clump together.

PV can lead to life-threatening complications if it’s not treated. Slower flowing blood and blood clots can keep oxygen from reaching your heart, brain, and other vital organs. As blood clots it can cause serious damage to your organs.

There is no known cure for PV, but the condition can be managed with treatment. Treatment focuses on routine blood draws and using medications to prevent serious blood clots. It’s important to talk to your doctor if you’re at risk for PV and experience any of its symptoms.

What Causes Polycythemia Vera?

Polycythemia vera is a rare disorder that occurs more often in men than in women, and rarely in anyone under 40. PV arises from a mutation in a protein called Janus kinase 2 (JAK2) caused by a gene (JAK2V617F) mutation. In its normal working state, JAK2 protein helps make blood cells, but in a mutated state, it causes an excessive amount of red blood cells. Mutations are changes or damage in the body’s DNA. DNA is responsible for all of your physical characteristics, from eye color to fingerprints. It’s not known what causes the gene mutation but in general, it is not thought to be inheritable (passed down from parents to children).

Red blood cells are made in your bone marrow. This production of blood cells is supposed to be tightly regulated. If you have PV, your bone marrow produces too many red blood cells.

Polycythemia vera symptoms

Early symptoms of PV often cause common physical ailments that may be easy to overlook them. But untreated PV may cause blood clots, which can lead to serious complications.

Common symptoms of PV include:



difficulties with activity

difficulties with concentration

abdominal discomfort

If the early symptoms of PV aren’t noticed, doctors may not discover the condition until a blood clot causes a serious complication. In these cases, the complication is the first sign that something is wrong.

Polycythemia vera causes and risk factors

Polycythemia vera is a rare blood disorder that occurs more often in men than in women. It’s rarely seen in anyone under age 40. PV is usually associated with a gene mutation called JAK2 V617F. The JAK2 gene handles production of a protein that helps make blood cells. About 95 percent of people with PV have this mutation.

Mutations are changes or damage in the body’s DNA. DNA is responsible for all of your physical characteristics, from eye color to fingerprints. The mutation that causes PV can be acquired, which means something has damaged the DNA (instead of being born with it) and passed on within families. More research needs to be done to understand what causes the genetic mutation behind PV.

If you have PV, the genetic mutation causes your bone marrow to produce too many red blood cells. The production of red blood cells within your bone marrow is normally tightly regulated. Having too many red blood cells in your bloodstream can cause the blood to clot and lead to dangerous complications.

If you have PV, your risk for developing serious complications depends on how likely you are to develop a blood clot.

Factors that increase your risk of developing blood clots in PV include:

history of previous blood clots

being over 60 years of age (for men)

high blood pressure



high cholesterol

Polycythemia vera diagnosis

If your doctor suspects that you might have PV, they will order a blood test called a complete blood count (CBC). A CBC measures the following factors in your blood:

the number of red blood cells

the number of white blood cells

the number of platelets

the amount of hemoglobin (a protein that carries oxygen)

the percentage of space taken up by red blood cells in the blood, known as the hematocrit

If you have PV, you will have a higher than normal hemoglobin and hematocrit. Along with other blood tests, you may also need a bone marrow biopsy to confirm the diagnosis.

Polycythemia vera treatment

PV is a chronic condition and can’t be cured. The only way to treat the disease is through management and prevention. Your doctor will prescribe a treatment based your risk for developing blood clots.

In low-risk people

Treatments for those at low risk include regular phlebotomy and low-dose aspirin. Phlebotomy is the removal of blood through a vein. Blood is withdrawn regularly and CBCs are run until there is a decrease in the number of red blood cells. Your doctor may also prescribe low-dose aspirin to decrease the risk of life-threatening blood clots.

In high-risk people

Hydroxyurea:Hydroxyurea is a chemotherapy drug that suppresses the production of red blood cells. This reduces the risk for clots and manages the disease, but can also increase the risk of leukemia. Over time, for about 1 in 4 individuals this drug can lose its effectiveness.

Using hydroxyurea for managing PV is off-label drug usage. It remains the recommended treatment for this condition in both the United States and Europe. Using a drug off-label means that the drug has been approved by the FDA for one purpose and is being used for a different purpose. Off-label use of drugs occurs when doctors have found them to be effective in patients. So, your doctor can prescribe a drug however they think is best for your care, especially when there is evidence that the drug works for a particular condition.

Interferon alpha:Interferon alpha can also be used off-label to manage PV, but it’s expensive and has a high risk of fever and flu-like side effects. Patients with certain mental health conditions should avoid this medication. It can also cause thyroid abnormalities.

In December 2014, the U.S. Food and Drug Administration (FDA) approved ruxolitinib (Jakafi) for the treatment of PV. This is currently the only FDA approved drug for PV. Doctors prescribe Jakafi to people who can’t tolerate hydroxyurea or whose blood counts have not responded to hydroxyurea. The medication works by inhibiting growth factors responsible for creating red blood cells and immune system functioning. Side effects may include:

lowering blood counts too much



increased risk of certain skin cancers

high cholesterol

Polycythemia vera complications

Doctors may not discover PV until after a blood clot causes a serious complication. These can be fatal. Blood clots can form in both arteries and veins. Complications of PV can include:

heart attack

deep vein thrombosis (DVT)

ischemic stroke, a stroke caused by loss of blood supply to the brain

pulmonary embolism, a blood clot in the lung

hemorrhagic death, death from bleeding, usually from the stomach or other parts of the digestive tract

portal hypertension, increased blood pressure within the liver

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