Polycythaemia Health Dictionary

A condition in which increased production of red blood cells leads to an unusually large number of them in the blood. This condition is usually caused by another disorder or by hypoxia, and is called secondary polycythaemia. If it occurs for no apparent reason, it is called polycythaemia vera or primary polycythaemia.

Secondary polycythaemia occurs naturally at high altitudes due to the reduced oxygen level. It can also result from a disorder that impairs the oxygen supply to the blood, or can be secondary to liver cancer or some kidney disorders. Descending to sea level, or effective treatment of an underlying disorder, returns the blood to normal.Polycythaemia vera is a rare disorder that mainly affects people over 40. The large number of red blood cells causes increased volume and thickening of the blood, which may lead to headaches, blurred vision, and hypertension. There may also be flushed skin, dizziness, night sweats, and widespread itching. The

spleen is often enlarged. Possible complications include a tendency to bleed easily or to form blood clots; stroke; and myelofibrosis or acute leukaemia (see leukaemia, acute).

Diagnosis is made from a physical examination and blood tests and by ruling out other causes. Treatment is by venesection, sometimes in combination with anticancer drugs or with radioactive phosphorus. This enables most patients to survive for 10–15 years.

A rise in the amount of HAEMOGLOBIN in the blood. This may be caused by an excess in the number of ERYTHROCYTES produced in the BONE MARROW or to a fall in the total volume of PLASMA in the circulatory system. It may also be a response to reduced oxygen levels – for example, among people living at high altitudes – or to liver or kidney disease: this type is called secondary polycythaemia.

The disorder may, however, occur for no obvious reason and is then called polycythaemia vera. This type develops mainly in people over 40 and about 400 people develop the disorder every year in the United Kingdom. The blood thickens, the sufferer may develop high blood pressure, ?ushing, headaches, itching and an enlarged spleen. A stroke may occur later in the disease process. Treatment of polycythaemia vera is by regular removal of blood by VENESECTION, sometimes in combination with an anticancer drug. Secondary polycythaemia is treated by remedying the underlying cause.

Polycythaemia rubra vera A disorder in which the red blood cells increase in number along with an increase in the number of white blood cells and platelets. The cause is unknown. Severe cases may require treatment with CYTOTOXIC drugs or RADIOTHERAPY.

n. an increase in the *packed cell volume (haematocrit) in the blood. This may be due either to a decrease in the total volume of the plasma (relative polycythaemia) or to an increase in the total volume of the red cells (absolute polycythaemia). The latter may occur as a primary disease (see polycythaemia vera) or as a secondary condition in association with various respiratory or circulatory disorders that cause deficiency of oxygen in the tissues and with certain tumours, such as carcinoma of the kidney.