Polycythemia vera (PV) is a chronic and progressive form of blood cancer. Early diagnosis can help decrease the risk of life-threatening complications, such as blood clots and bleeding problems.

The discovery of the JAK2 genetic mutation, JAK2 V617F, has helped doctors diagnose people with PV. About 95 percent of those who have PV also have this genetic mutation.

The JAK2 mutation causes red blood cells to reproduce in an uncontrolled manner. This causes your blood to thicken. Thickened blood restricts its flow to your organs and tissue. This can deprive the body of oxygen. It can also cause blood clots.

Blood tests can show if your blood cells are abnormal or if your blood count levels are too high. White blood cell and platelet counts can also be affected by PV. However, it’s the number of red blood cells that determines the diagnosis. A hemoglobin greater than 16.0 g/dL in women or greater than 16.5 g/dL in men, or a hematocrit greater than 48 percent in women or greater than 49 percent in men can indicate PV.

Experiencing symptoms may be a reason to make an appointment and have a blood test. These symptoms can include:

If your doctor thinks you have PV, they’ll refer you to a hematologist. This blood specialist will help determine your treatment plan. This usually consists of periodic phlebotomy (blood drawing), along with a daily aspirin and other medications.

PV puts you at risk for a variety of complications. These can include:

Thrombosis

Thrombosis is one of the most serious concerns in PV. It’s the clotting of blood in your arteries or veins. The severity of a blood clot depends on where the clot has formed. A clot in your:

Enlarged spleen and liver

Your spleen is in the upper left part of your abdomen. One of its jobs is to filter worn out blood cells from the body. Feeling bloated or easily full are two symptoms of PV triggered by an enlarged spleen.

Your spleen becomes enlarged when it tries to filter out the excessive number of blood cells your bone marrow creates. If your spleen doesn’t return to its normal size with standard PV treatments, it may have to be removed.

Your liver is in the upper right part of your abdomen. Like the spleen, it can also become enlarged in PV. This can be because of a change in blood flow to the liver or the extra work the liver has to do in PV. An enlarged liver can cause abdominal pain or extra fluid to build up in the abdomen.

High levels of red blood cells

The increase of red blood cells can cause joint swelling, problems with concentration, headaches, vision problems, and numbness and tingling in your hands and feet. Your hematologist will suggest ways to treat these symptoms.

Periodic blood transfusions may help keep red blood cells at an acceptable level. When this option doesn’t work or medications are not helping, your doctor may recommend a stem cell transplant to manage the disease.

Myelofibrosis

Myelofibrosis, also called the “spent phase” of PV, affects around 15 percent of those diagnosed with PV. This occurs when your bone marrow no longer produces cells that are healthy or function properly. Instead your bone marrow is replaced with scar tissue. Myelofibrosis not only affects the number of red blood cells, but your white blood cells and platelets too.

Leukemia

Long-term PV can lead to acute leukemia, or cancer of the blood and bone marrow. This complication is less common than myelofibrosis, but its risk increases with time. The longer an individual has PV, the higher the risk of developing leukemia.

PV treatment can also cause complications and side effects.

You may begin to feel tired or fatigued after a phlebotomy, especially if you’re having this procedure frequently. Your veins may also become damaged from having this procedure repeated.

In some cases, a low-dose aspirin regimen can lead to bleeding.

Hydroxyurea, which is a form of chemotherapy, can lower your red and white blood count and platelets too much. Hydroxyurea is an off-label treatment for PV. This means that the drug is not approved for the treatment of PV, but it has been shown to be useful in many people. Common side effects of hydroxyurea treatment in PV can include abdominal pain, bone pain, and dizziness.

Ruxolitinib (Jakafi), the only FDA approved treatment for myelofibrosis and PV, can also suppress your total blood counts too much. Other side effects can include dizziness, headache, fatigue, muscle spasms, abdominal pain, difficulty breathing, and itching.

If you experience significant side effects from any of your treatments or medications, talk to your medical team. You and your hematologist can find the treatment options that work best for you.