Polycythaemia Vera

What Is Polycythaemia Vera?

Commonly known as PV, polycythaemia vera is an uncommon blood disorder that causes the body to produce an excess amount of red blood cells. The additional red blood cells cause the blood to thicken, making it flow through the body slower than usual. Thicker blood can cause clots to develop in the small blood vessels, which can contribute to heart attacks and strokes.

Blood cells are produced in the bone marrow (the soft tissue found inside the bones), in which white blood cells and red blood cells are created. White blood cells are responsible for fighting infections and producing platelets (these help the blood to clot). PV leads to an excess of red blood cell production in the bone marrow, and the bone marrow may also produce an increased number of platelets and white blood cells as a result.

Red blood cells are also called erythrocytes and RBCs. Normal, healthy red blood cells are shaped like hole-less doughnuts and usually live for around 120 days, before being replaced with new red blood cells. These cells carry the iron-rich protein haemoglobin, which is responsible for transporting oxygen around the body. Haemoglobin gives red blood cells their colour. Red blood cells play an important role in the removal of carbon dioxide from the cells, as they carry the waste product carbon dioxide to the lungs, where it is exhaled.

Important information

Polycythaemia vera is a chronic, rare disorder which can be serious and potentially fatal if left untreated. The reason for the disorder is unknown. PV tends to develop gradually and often does not cause any symptoms for a number of years. The symptoms of PV can be general and, as a result, it can take time to diagnose the condition. In many cases the condition is diagnosed during tests for other diseases. PV is most common among men aged over 60 and uncommon in young people.

PV causes the blood to become thicker, which slows the rate at which it travels around the body. This can increase the likelihood of blood clots, as arteries and veins can become obstructed. The slowed blood flow decreases the sum of oxygen transported to organs and tissues, leading to potential problems such as angina, dizziness, headaches, itching, vision problems, gout and heart failure. The condition can also cause kidney stones and stomach ulcers.

It is possible for certain individuals with PV to develop myelofibrosis, which is a condition that causes the bone marrow to be replaced with scar tissue (fibrous tissue). The abnormal cells grow quickly and can contribute to acute myelogenous leukaemia (AML), a form of cancer that can advance quickly. In people with AML there is a surplus of immature white blood cells within the bone marrow and the blood.


There is no cure for PV, but it can be managed effectively when diagnosed and treated early. It is vital that people who have relevant symptoms see their doctor as early as possible. Many individuals with PV do not require intensive treatment, but when this is needed it can usually deal with the condition effectively and lower the threat of blood clots, strokes and heart attacks.

Polycythaemia vera’s other names

  • Primary polycythaemia.
  • Polycythaemia rubra vera.
  • Erythremia.
  • Vaquez disease.
  • Splenomegalicn polycythemia.
  • Osler disease.
  • Myeloproliferative disorder.
  • Erythrocytosis megalosplenica.
  • Polycythaemia with chronic cyanosis - myelopathic polycythaemia.
  • Cryptogenic polycythaemia.

What are the causes of polycythaemia vera?

The condition is sometimes referred to as primary polycythemia and occurs because of a change in DNA. DNA is the material found in all living cells and contains genetic information. Changes in the DNA are known as mutations, and PV is caused by a mutation of the JAK 2 gene. This gene contains important information about a significant protein in blood cell production. Physicians and scientists do not fully understand what leads to the JAK 2 mutation. However, they know it happens after conception and that children do not get the condition from their parents. The mutation cannot be overturned.

A second form of polycythemia also exists, not linked to the JAK 2 gene, and it is known as secondary polycythemia. This is brought on by a long-term reduction in oxygen levels. A shortage of oxygen in the body can cause the production of a protein called erythropoietin (EPO), which increases red blood cell production and thickens the blood. Individuals who smoke and those that spend long periods of time at high altitude may also be diagnosed with secondary polycythemia. It is possible to cure secondary polycythemia, but this depends if the primary reason can be successfully treated.

Who is most at risk of polycythaemia vera?

This is a rare condition and there are only five new cases per one million people ever year. The condition is more frequent in men over the age of sixty, but it can also be found in younger people. It is rare for the disorder to affect people under the age of twenty. Males are more likely to develop PV in comparison to females.

What are the symptoms and signs of polycythaemia vera?

Polycythaemia vera tends to develop gradually and symptoms may not be present for many years. PV symptoms are caused by increased thickness of the blood and a subsequent decrease in the speed of blood flow. As a consequence of this not enough oxygen is transported around the body, and this can lead to incorrect function of the organs.

Common signs of PV:

  • Dizziness.
  • Headaches.
  • Weakness.
  • Enlarged spleen (which causes discomfort on the left section of the abdomen).
  • Blind spots.
  • Redness in the face.
  • Bleeding gums.
  • Itching all over the body (this is usually worse after bathing).
  • Shortness of breath.
  • Burning feeling in the skin.
  • Inexplicable weight loss.
  • Unusual bleeding.
  • Difficulty breathing when lying down.
  • Pain in the bones (this is rare).

Potential complications

If you suffer with PV the increased thickness of the blood can cause serious problems. When the blood is thicker it cannot travel around the body as easily, meaning the speed of blood flow is reduced. This can result in blood clots, being the most dangerous complication associated with PV. Blood clots obstruct blood flow, which can bring about strokes and heart attacks. Blood clots can also cause the spleen and liver to become enlarged, leading to the development of severe pain. PV can also be a source of gout, kidney stones and stomach ulcers.

How do you diagnose polycythaemia vera?

Many people can have PV a long time before they display any symptoms. It is common for the condition to be diagnosed during screening tests for other conditions. If you do not have symptoms, but your levels of haematocrit and haemoglobin are high, there is the likelihood that your doctor will suggest further tests.

PV is diagnosed following physical examinations, medical and family history and diagnostic tests, which can include bone marrow and blood tests. When you visit your doctor they will ask you questions about your symptoms and medical history. You will be encouraged to provide information on your symptoms, underlying medical conditions, problems in the past and any medication you are taking or have taken recently. You will also be asked questions about allergies.

During a physical examination the doctor will search for symptoms of PV, including an enlarged spleen, redness on the skin and bleeding gums. Where the physician verifies a PV diagnosis, they will determine if the condition is primary or secondary. A physical examination and medical history can usually determine the type of PV, but additional tests may be required. These include:

  • Complete blood count (CBC): the CBC provides a lot of useful information. The test measures the levels of the three blood cell types; white blood cells, platelets and red blood cells. If the quantity of red blood cells is larger than usual this may indicate PV. PV can also increase the number of platelets and white blood cells.
  • The CBC calculates haemoglobin levels. Haemoglobin is an iron-rich protein, which is responsible for carrying oxygen around the body. If the haemoglobin levels are more elevated than average this may indicate PV.
  • The haematocrit result shows the proportion of blood made up of red blood cells, and if the haematocrit level is high this may indicate PV.

Further blood tests:

  • Blood smear: a blood smear involves looking at a blood sample using a microscope, which enables doctors to gain insight into the size and profile of the red blood cells. The sample will be checked for an elevated density of red blood cells and abnormal cells, which can be caused by myelofibrosis or similar conditions associated with PV.
  • Arterial blood gas test: this is where a blood sample is gathered from the artery, to gauge the levels of oxygen and carbon dioxide in the blood and determine the pH (acidity) of the blood. Where levels of oxygen are reduced this may indicate PV.
  • EPO level: this test measures the sum of EPO, which is a hormone used for the stimulation of blood cell production by the bone marrow. If the levels of EPO are lesser than average this may indicate PV.
  • Red blood cell mass: normally undertaken at the nuclear medicine section of a hospital. The test involves a blood sample and mixing it with a radioactive dye, which attaches to the plasma and blood cells. The attached cells are then returned to the bloodstream via an injection. A further sample is taken and technicians can determine the total amount of red blood cells in the body. If the level is higher than usual this may indicate PV.

In certain cases doctors may advise an aspiration test or biopsy of the bone marrow. A biopsy involves a minor surgical operation, while aspiration is the use of a fine needle to remove fluid from the bone marrow. Bone marrow tests are designed to check the function of the bone marrow. If results show bone marrow is generating excess blood cells, this may be an indication of PV.

How can you treat polycythaemia vera?

A range of treatments may be used to treat polycythaemia vera, including medication, phlebotomy and biological therapy.

Aims of treatment

There is no cure for PV, though there are treatments that can control the condition. These are able to lower the chances of complications, such as heart attacks and strokes. The aim of treatment is to lower the threat of complications, by reducing the red blood cell numbers and lessening the thickness of the blood. When the blood is a normal thickness it can flow through the vessels more freely, helping to prevent clots from forming and enabling oxygen to reach all the organs. When the blood is at its normal thickness symptoms, including dizziness and weakness, will usually ease.

Research indicates that successful handling of PV enables people to live long, healthy lives.

Specific treatments


This is where blood is taken in the same way as donating blood. A needle is introduced into the vein and pulled back, causing blood to collect in a sterile sealed tube or bag. Phlebotomy decreases the quantity of red blood cells found in the body, reducing the thickness of the blood and allowing blood to flow freely around the body. Around one pint of blood (one unit) is taken per week until the haematocrit level is normal. Once levels have returned to normal they will be monitored closely, and a phlebotomy may be carried out every two to three months as required.


Your physician may also prescribe medication designed to stop the bone marrow from producing an excess of red blood cells. One of the medicines used is hydroxyurea, a chemotherapy drug that is often given to cancer patients. This drug is designed to lower the level of platelets and red blood cells in the blood, decreasing the thickness of the blood and speeding up blood flow. If you suffer from bone pain you may be advised to take aspirin, which is also used to lower the threat of blood clots.

Immunotherapy (biological therapy)

This uses chemicals found in the body to encourage the immune system to act against the excessive manufacture of red blood cells. If you suffer from PV your physician may opt to use interferon-alpha, which is naturally produced by the body to try and bring red blood cell numbers down and reduce the thickness of the blood.

Other treatments

Other treatments may be used to ease symptoms such as itching. Treatments for itching may include antihistamines, UV light treatment or medications, which may include cimetidine, psoralen, cyproheptadine and cholestyramine. If you have high levels of uric acid in the blood, allopurinol may be prescribed.

Your physician may make the decision to prescribe radioactive phosphorus to curb the excessive actions of the bone marrow, lower the quantity of red blood cells and decrease the thickness of the blood.

How can you prevent polycythaemia vera?

It is not possible to prevent Polycythaemia vera. However, the right course of management and treatment can control the condition effectively. It may be possible to prevent secondary polycythemia in certain cases, which requires the reduction of levels at which the body is exposed to lowered oxygen. This may require giving up activities such as mountain biking, climbing and to avoid smoking. People who have serious lung and heart problems may be at risk of secondary polycythemia. Treating the primary cause can help to ease symptoms in this case. Having a good, healthy lifestyle can also help to prevent secondary polycythemia.

How to live with polycythaemia vera

Avoiding complications

You can suffer with PV for some time before you start to notice any symptoms, but it is a good idea to visit your doctor on a regular basis. This is especially the case if you notice symptoms – the earlier the condition is diagnosed and treated the better. Exercise can help to improve your circulation and lower the chances of clotting, and you can ask your doctor about suitable exercises.

People with PV often experience itchy skin. If this is the case try not to scratch, as this can damage the skin. Ask your doctor for advice about reducing itchiness and avoid using perfumed shower gel or bubble bath. Use cool water when you wash and carefully dry your skin.

People with PV generally have poor circulation, which means that they are susceptible to injury when exposed to extreme temperatures.

  • When you leave the house, wrap up warm and pay attention to your hands, head and feet.
  • If it is hot outside protect your skin by wearing sun cream, a hat and avoid using sun-beds.
  • Protect yourself when playing contact sports.
  • Keep an eye on your feet and see your doctor if you notice any changes or experience discomfort.

Ongoing healthcare needs

People with PV have need of frequent medical treatment and their condition will be monitored closely by their care team. It is vital that patients see their doctor on a regular basis, so they can treat any problems before they get worse. Doctors will carry out regular blood tests. If you are prescribed medication for PV it is imperative that you follow the dosage instructions.

Support groups

Support groups are often a source of advice, information and emotional support. Ask your doctor for information on support groups or organisations that may be of assistance in your local area.

Key facts

  • Polycythaemia vera (PV) is an uncommon, chronic blood disorder. It causes the body to produce an excess amount of red blood cells. The surplus red blood cells cause the blood to become thicker, which increases the risk of clotting and has the potential to cause heart attacks and strokes.
  • Primary polycythaemia is caused by a JAK 2 gene mutation. However, the source of the JAK 2 mutation is unknown.
  • Secondary polycythemia is the result of prolonged exposure to low oxygen levels. This form of the condition is not linked to the JAK 2 gene.
  • PV is an uncommon disorder of the blood and most frequently occurs in men aged over 60.
  • The most frequent signs of PV are headaches, double or distorted vision, itching, an enlarged spleen, dizziness, weakness and inexplicable loss of weight. 
  • A PV diagnosis is made based on apparent signs, medical history, diagnostic tests and physical examinations.
  • The aims of treatment are to lower the quantity of red blood cells and the thickness of the blood.
  • Treatments for PV include phlebotomy (taking blood from a vein to decrease the quantity of red blood cells), medication and biological therapy.
  • It is not possible to prevent PV – though treatment can help to lower the danger of complications and ease symptoms. Secondary polycythemia can often be avoided by avoiding exposure of the body to low oxygen levels for long periods of time.
  • People with PV require lifelong medical care. This often involves regular checks and taking medication, though many people do not require intensive treatment.
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