Polycythaemia Vera

Clinical picture

Polycythaemia Vera (PV) means 'true (Vera) disease with an excess (poly) of blood cells (cytemia)' and the illness is also known under the names Vasquez disease, Vasquez-Olser, primary polyglobuly and primary erythrocytosis. PV is one of the myeloproliferative disorders that is characterised by the production of too many red blood cells. This is also known as uncontrolled cell growth. Normally this production is restricted, but in the case of PV, cells are continuously produced due to a mutation in a specific gene (called JAK2). Most of the patients do not only have too many red blood cells, but also suffer from too many white bloods cells and platelets.

Due to the large amount of red blood cells, the blood becomes thicker. This makes it less likely to flow through the small blood vessels leading to an increased risk of blood clots in the veins (venous thrombosis) or in arteries (arterial thrombosis). Two-thirds of PV patients also have an increased number of platelets (thrombocythaemia).

How many patients suffer from PV?

Polycythaemia vera is a rare disease with approximately 0.6–2.8 new patients per 100,000 European citizens each year. Although PV is more common in older patients, younger patients can also be affected by this disease. The average age at time of diagnosis diagnosis is between the 55 to 60 years, and is more common in men than in women.

Symptoms

The complaints experienced by patients with PV are caused by the increased thickness of the blood and increased number of platelets (thrombocytopenia). The symptoms can vary greatly between patients, from headaches, dizziness, heart complaints and bleeding to excessive perspiration and itching.

• Pain attacks in the abdomen, due to the disturbed blood circulation in the abdominal cavity
• Tingling and pain in the hands, fingers, feet or toes
• Spontaneous haemorrhages due to the increase in immature platelets
• Problems with blood circulation (headache, dizziness, fatigue)
• Vision problems (blurred vision, observing flashes of light or spots)
• Itching, rash
• Gout
• An enlarged spleen due to the fact that more red blood cells are withdrawn from the bloodstream. As the liver and spleen continue to develop, the appetite of the patients could decrease.
• Kidney stones, due to the increased level of substances that are released during the breakdown of the red blood cells.
• Phlebotomy
• Thrombosis

A serious complication of the increased thickness of the blood is thrombosis. This creates blood clots that can clog veins in the body. This increases the chance on a stroke (cerebral infarction), myocardial infarction, thrombosis (venous thrombosis) or pulmonary embolism. Problems with the blood coagulation are more common in people over 60, or those who have previously experienced blood clots.

Cause

The cause of polycythaemia vera remains unknown, although in 97% of the patients a mutation in the material of stem cells (mutation) is found. This so-called JAK2 mutation causes the uncontrolled growth and division of stem cells. This creates a surplus of blood cells, including the number of red blood cells. Some patients also suffer from an increase in white blood cells and platelets. A JAK2 test may be useful for classification and treatment.

Diagnosis

In order to be able to diagnose polycythaemia vera, several studies can be performed:

• Structured patient history, taking into account the signs and symptoms the patient presents with.
• Physical examination, spleen size, skin rash (urticaria).
• Extensive blood tests for determining red and white blood cell and platelet levels.
• Bone marrow test (cristabiopsis and sternum function).
• Ultrasound of liver, spleen and kidneys.
• Genetic research on the JAK2 mutation: this mutation occurs in 97% of patients with PV.

Treatment

Polycythaemia vera cannot yet be cured. However, with treatment, PV patients have a normal life expectancy. Complications as a result of the increased thickness of the blood are the most important risks. In some cases, some patients develop myelofibrosis and 5% acute myeloid leukaemia. However, with the right treatment the prognosis is pretty good.

Based on the symptoms and test results, patients are assigned into three groups:

• Low risk: younger than 60 years, no history of thrombosis, no risk factors for the development of cardiovascular disease and the platelet content is lower than 1500 x 10⁹ / l blood.
• Intermediate (average) risk: the patient does not fall within the low and not within the high-risk group.
• High risk: older than 60 or has a history of thrombosis.

For patients in the low-risk group, in most of the cases is chosen for watchful waiting. In the case of intermediary and high risk, the treatment focuses on combating complications and reducing complaints. The goal is to reduce the red blood cell count and thus reduce the risk of thrombosis.

Treatment may also consist of:

• Acetylsalicylic acid (aspirin or ascal) to prevent thrombosis formation.
• Bloodletting (phlebotomy): by bleeding, the number of red blood cells decreases and the blood becomes thinner and easier to pass though the veins and arteries. This is performed in the same way as when donating blood. Often 250-500 ml of blood is drained weekly in the beginning, as the disease progresses this decreases to once every 1 to 3 months.
• Chemotherapy with hydroxycarbamide: this agent inhibits cell growth by reducing the activity of the bone marrow.
• Erythrocytapheresis: The patient’s blood is removed from circulation, passed through a extracorporeal machine that filters the blood to remove excess red blood cells, and is then returned back to the patient’s circulation via infusion.
• Immunotherapy with interferon Alfa: this stimulates the immune system and inhibits cell growth. In addition, it will also decrease the itching that occurs with PV.

Additional information

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