Polycythemia vera (PV), also called polycythemia rubra vera, is a myeloproliferative neoplasm (MPN) where the body makes too many red blood cells. Sometimes there are too many white blood cells or platelets made as well. The excess blood cells build up in the blood, making it thicker so that it flows slower than normal. Thick blood increases the risk of bleeding problems and blood clots, and blood clots increase the risk of a stroke or heart attack. They can also cause a blockage in the lungs or in the arteries of the legs or arms. The
PV is most commonly diagnosed in people 60 to 65 years of age. It isn't common in people under the age of 40. More men than women develop PV, but women are diagnosed more often at a younger age.
Most people with PV have a change, or mutation, in the JAK2 (Janus kinase 2) gene. These gene mutations happen during a person's lifetime (they are not inherited or present at birth). The JAK2 gene makes a protein that controls the number of red blood cells, white blood cells and platelets. But when the gene is changed, the body makes more blood cells than normal. The JAK2 gene also causes the body to make too many cytokines, a type of protein that controls the immune system. Your healthcare team may order molecular tests to look for JAK2 gene changes if they suspect you have PV.
PV may not cause any signs or symptoms in its early stages. It's often diagnosed with a blood test done for other health reasons. Symptoms start when too many red blood cells and platelets build up in the blood. These symptoms can cause problems, or complications, as the disease develops. The most common symptoms of PV are fatigue and weakness, blurred vision, and easy bruising or bleeding such as frequent nosebleeds.
Your healthcare team will create a treatment plan just for you. Treatment is based on your symptoms, how quickly PV progresses, your age and your overall health.
The goal of treatments for PV is to control symptoms and lower the risk of complications. Treatments can be done to:
- thin the blood when there are too many red blood cells
- prevent bleeding
- stop blood clots
A phlebotomy is the removal of blood from the body, such as blood taken for diagnostic tests. A therapeutic phlebotomy removes larger amounts of blood in order to treat disease. It is used with PV to make the blood thinner because there are too many red blood cells making the blood thick. A phlebotomy is usually the first treatment for people with PV. It may be the only treatment needed for many years.
Your healthcare team may tell you to drink extra fluids before and after having a therapeutic phlebotomy. This helps with the removal of the blood and helps to reduce side effects.
A therapeutic phlebotomy is done in the same way as donating blood. A needle is inserted into a vein to remove blood. The needle is connected to a tube leading to a bag that collects the blood. Your healthcare team will decide how much blood needs to be removed, but it is usually between 250 mL and 500 mL. You may also be given a saline solution to stop a drop in blood pressure caused by the blood removal.
Blood is taken every 1 to 2 weeks, or more often, until the number of red blood cells goes down. Your healthcare team will use regular blood tests to watch the number of red blood cells in your blood.
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Drug therapy may be used to lower red blood cell or platelet counts. The following drugs may be used to treat PV:
hydroxyurea (Hydrea) – most commonly given
- ruxolitinib (Jakavi) – may be offered if you have been taking hydroxyurea and still need a phlebotomy
For more information on certain drugs, go to sources of drug information.
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Supportive therapy is an important part of treatment for PV. It is given to treat or prevent the complications that usually happen with the disease.
Low dose acetylsalicylic acid (ASA, or Aspirin) is given to lower the risk of a blood clot. ASA makes platelets less likely to stick to the wall of an artery and build up to form a clot. This helps reduce the risk of a stroke or heart attack. Your healthcare team may suggest other ways you can reduce this risk, including quitting smoking.
Allopurinol (Zyloprim) is used to lower the level of uric acid in the blood. Uric acid is made by the body when it breaks down chemicals called purines. Purines are made by damaged or dying cells in the body. The high number of red blood cells caused by PV means that there is more uric acid made when the body breaks down the red blood cells. High levels of uric acid can cause a painful inflammation of the joints called gout. It most often affects the joint of the big toe.
Antihistamines may be given to relieve itchy skin. If antihistamines don't relieve the itching, your healthcare team may try an antidepressant to treat itching. The dose given to treat itching is much lower than the dose given to treat depression. Some antidepressants that may be used are sertraline (Zoloft), fluoxetine (Prozac) or citalopram (Cipralex).
Surgery to remove the spleen (called a splenectomy) is sometimes done if an enlarged spleen does not respond to other treatments and is causing pain.
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Follow-up after treatment is an important part of cancer care. Follow-up for PV is often shared among the blood specialists (hematologists) and your family doctor. Your healthcare team will work with you to decide on follow-up care to meet your needs.
Don’t wait until your next scheduled appointment to report any new symptoms and symptoms that don’t go away.
Kareem Jamani, MD, LMCC, FRCPC
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