This information is about polycythaemia vera (PV), which is one of a group of conditions known as the chronic myeloproliferative diseases (CMPDs).

The myeloproliferative diseases are a group of conditions affecting the function of the bone marrow. They involve an overproduction of one or more of the types of blood cells that are produced there. The chronic myeloproliferative diseases are related to cancer and, rarely, they may develop into a form of leukaemia.

The main types of chronic myeloproliferative disease are:

• essential thrombocythaemia 
• polycythaemia vera
• idiopathic myelofibrosis.

Chronic myeloid leukaemia (CML) is also a myeloproliferative disease although it is usually dealt with as a separate condition.

This is the spongy material in the centre of some of our bones. It produces cells known as stem cells. Stem cells are immature cells that develop into three different types of blood cells:

• red blood cells carry oxygen to all cells in the body
• white blood cells fight infections and form part of our immune system
• platelets help the blood to clot, to prevent bleeding.

PV is a myeloproliferative disorder in which too many red blood cells are produced by the bone marrow, without any obvious cause. Some people have a faulty gene, called the JAK2 gene, that may have caused their condition. Finding this faulty gene can help to make the diagnosis. Having too many red blood cells results in a raised level of haemoglobin (Hb) (the opposite of anaemia).

There are other types of polycythaemia that may be secondary to another disease or condition, such as lung disease, living at high altitude, or dehydration. The treatment of these other types of PV is very different, and usually involves treating the underlying condition.

Too many red blood cells can make the blood much thicker than normal. Some people with PV also have increased numbers of white cells and platelets in their blood.

Like other myeloproliferative diseases, PV is a rare condition. It mainly occurs in adults aged over 40, and is rare before this age. The causes of PV are unknown.

Having a high number of red cells in the blood does not always cause symptoms, and some people are diagnosed with PV after a routine blood test for something else.

A high number of red cells in the blood makes the blood thicker than normal and affects the way it flows. This is known as hyperviscosity. Symptoms of hyperviscosity include headaches, blurred vision, breathlessness, and confusion. Some people may also notice that their skin appears much redder than normal. An abnormal red complexion is called plethora.

Other symptoms include sweating and itching, especially after a bath. A small number of people with PV may develop gout, which is a condition caused by the breakdown of high numbers of red blood cells. Gout causes inflammation and pain in the joints, usually of the big toe, and less often in the ankles, hands or knees.

A high level of red blood cells, or platelets, may cause the blood to clot. Clots (thromboses) can form anywhere in the body, and the symptoms will depend on which part of the body is affected. Common sites for a clot to form are:

• The deep veins of the leg – this can cause symptoms such as pain, swelling, heat, and redness in the calf (known as deep vein thrombosis or DVT).
• The brain – this may cause mild symptoms such as headaches, sight disturbances, or dizziness. Blood clots in the brain may also cause symptoms that are more serious, such as a stroke or TIAs (transient ischaemic attacks [mini-strokes]).
• The heart – a blood clot in the heart may cause chest pain, and in severe cases, can result in a heart attack.
• The lungs – a blood clot in the lung may cause breathlessness and chest pain. This is known as pulmonary embolism.

As well as causing clotting problems PV very occasionally causes abnormal bleeding. This can cause symptoms such as:

• nosebleeds
• bruising
• abnormal vaginal bleeding
• bleeding gums.

If you develop any of these symptoms between your appointments, you should discuss them with your haematologist.

PV is usually diagnosed by a haematologist (specialist in blood disorders). Diagnosis is often made following a blood test called a full blood count. This counts the number of the red cells, white cells and platelets. In PV, there is a high red blood cell count. You may also have a blood test to check for the JAK2 gene.

Other conditions can cause an increased red blood cell count. These need to be ruled out before a diagnosis of PV can be made.

The tests and investigations that may be done to confirm a diagnosis of PV are:

Red cell mass study This involves mixing a sample of your blood with a mildly radioactive dye, which is then injected into a vein in your arm. The mixture of your blood and the radioactive dye then circulates around your body. A second sample of blood is taken some time later, and the doctors are able to determine the total mass of your red blood cells. The fluid in your blood (plasma) that contains all the blood cells is also measured. By comparing the two results, the doctors can tell if you have an increased number of red blood cells in your blood or a reduced amount of plasma. Both of these would increase the concentration of the blood, but for a diagnosis of PV there needs to be an increased number of red blood cells only.

Bone marrow biopsy This involves taking a sample of bone marrow from the back of the hip bone (pelvis), or occasionally the breast bone (sternum). The sample is then looked at under a microscope to see if it contains any abnormal cells.

The bone marrow sample is taken under a local anaesthetic. You are given a small injection to numb the area, and a needle is passed gently through the skin and into the bone. A tiny sample of the marrow is then drawn (aspirated) into a syringe (a bone-marrow aspirate). Sometimes a small core of marrow is also needed (a trephine biopsy) and this takes a few minutes longer. This procedure can be painful for a few seconds, and you may feel some discomfort for a few hours afterwards.

Other tests and investigations may also be needed to confirm that the high levels of red blood cells are caused by PV, and not some other condition. These might include: a chest x-ray, and an ultrasound scan of the abdomen to look at the kidneys, liver and spleen. Your spleen may be enlarged, as it is involved in the breakdown of red blood cells.

The aim of treatment is to reduce the number of red blood cells in the blood, and therefore reduce the risk of any complications occurring. Treatment will depend upon how many red blood cells you have, your age, whether you have symptoms caused by the disease and whether you have a high platelet count. Often treatment is individually planned. If you have been diagnosed with PV but it is not causing you any problems, you may not need any treatment for a while.

Venesection is one of the simplest ways to reduce the number of red blood cells. It involves removing some of your blood by inserting a needle into a vein. Usually, about a pint of blood is removed at a time. This procedure can be repeated if necessary. Venesection can help to keep down the number of red blood cells but it will not affect the number of platelets. Each time some blood is removed, you will be asked to drink plenty of fluids to replace what you have lost.

Low-dose aspirin can help to prevent clots because it affects the way that platelets 'stick together'. Some people may be prescribed it as part of their treatment. One of the side effects of aspirin is an increased risk of bleeding, and ulcers in the stomach. You will be advised to use other simple painkillers, like paracetamol, should you need them.

Chemotherapy Chemotherapy is the use of anti-cancer (cytotoxic) drugs to destroy cancer cells. Hydroxycarbamide, is a chemotherapy tablet that can help to reduce the blood cell count. It can cause side effects, although generally these will be mild. Side effects can include a lowered resistance to infection, anaemia, feeling sick (nausea), mouth ulcers, and diarrhoea. It can also affect fertility. People taking hydroxycarbamide are advised not to get pregnant or father a child, as there may be a risk of harming the developing foetus. It is advisable to use adequate contraception while taking the drug and also for a few months afterwards. If used over a long period of time, hydroxycarbamide may increase the chance of the PV developing into a leukaemia.

The chemotherapy drug busulfan may also be used. However this drug is used less often than hydroxycarbamide. Busulfan is usually given as a tablet but can be given as an injection into a vein. Its side effects are similar to those of hydroxycarbamide.

Interferon-alpha Interferon is a substance that occurs naturally in the body (but can also be man-made). It stimulates the body’s defence system. Interferon is given as an injection under the skin, usually three times a week. Side effects include flu-like symptoms, dizziness, and extreme tiredness (fatigue).

Radioactive phosphorus (32P) may be used in some situations. Radioactive phosphorus is given as an injection. It irradiates the bone marrow and can lower the number of platelets being produced.

Allopurinol is used to treat the gout that some people experience with PV. Inflammation of the joints can often be successfully treated with painkillers.

Stem cell or bone marrow transplant (from a donor) Rarely, this intensive treatment is used for younger people with certain kinds of PV. It involves replacing stem cells (early blood cells) which have been destroyed by high doses of chemotherapy. After the treatment, you are given stem cells from a donor (usually a brother or sister).

Your doctor or nurse will explain your treatment to you and should answer any questions that you have.

Research into new ways of treating PV is ongoing. Doctors use clinical trials to assess new treatments.

Before any trial is allowed to take place, it must be approved by a research ethics committee, which protects the interests of those taking part. Before you enter a trial, your doctor or research nurse must discuss the treatment with you so that you have a full understanding of the trial and what it involves. You may decide not to take part, or to withdraw from the trial, at any stage. You will then receive the best standard treatment available.

You will need to have regular check-ups and blood tests. These will probably be ongoing. If you have any problems, or notice any new symptoms in between these times, let your nurse or doctor know as soon as possible.

The need for practical and emotional support will of course be individual. Some people with PV may find that their life is largely unaffected; for others the condition may be a source of great fear and distress.

You may feel many different emotions, including anger, resentment, guilt, anxiety and fear. These are all normal reactions, and are part of the process many people go through in trying to come to terms with their condition and its treatment.

You don’t have to cope with these feelings on your own; people are available to help you. Some hospitals have their own emotional support services with specially trained staff, and some of the nurses will have received training in counselling. Cancerbackup can put you in contact with counselling services in your area.

This section has been compiled using information from a number of reliable sources, including:

• Polycythaemia (Erythrocytosis) and Polycythaemia Vera. Dr C Harrison and Prof S Machin. www.netdoctor.co.uk
• Wintrobe’s Clinical Haematology (11th edition). Eds Lee et al. Williams and Wilkins, 2004.
• Essential Haematology (5th edition). Eds Hoffbrand et al. Blackwell Scientific Publications, 2006.

For further references, please see the general bibliography.