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POLYCYTHAEMIA

What is Polycythaemia ?

Polycythaemia literally means too many cells . It is used to describe a condition where there are too many red blood cells in the blood. People with polycythaemia often have a high colour. The increase in red cells makes the blood thicker than usual and the blood circulates more slowly. This can sometimes cause blood clots (thrombosis), headaches or trouble with the eyesight. There are different types of polycythaemia and other symptoms can occur depending on the type. The different types are: secondary polycythaemia, primary polycythaemia and relative polycythaemia. Each has a different cause and treatment is different in each case.

How does Polycythaemia occur ?

SECONDARY POLYCYTHAEMIA In this condition the bone marrow makes more red cells than normal as a result of a disorder elsewhere in the body, such as chronic lung disease. In healthy people, a hormone called erythropoietin (EPO) has the responsibility for stimulating the marrow to make red cells. EPO is made by the kidney. When the body is short of oxygen the kidney automatically makes more EPO. The marrow then makes more red cells to carry oxygen. Chest disease (by lowering oxygen levels) can therefore lead to secondary polycythaemia. Surprisingly, disorders of the kidney can also result in excessive (rather than reduced) EPO production. This leads to secondary polycythaemia as well.

PRIMARY POLYCYTHAEMIA OR POLYCYTHAEMIA RUBRA VERA (PRV) In this condition the bone marrow is making too many red cells without any reason. It does not involve a problem with EPO. It is therefore a disorder of the bone marrow. Sometimes the marrow also makes too many white blood cells and platelets (small cells in the blood which help blood clotting). The spleen may be enlarged and felt as a lump in the left of the abdomen. Gout can occur, and skin itching is quite common. Even if there are too many platelets, they may not work properly, and this can lead to bruising. On the other hand, too many platelets can also increase the risk of blood clots and small strokes. PRV is commonest in people over 50 years of age.

RELATIVE POLYCYTHAEMIA Blood is a mixture of cells and a fluid called plasma. Normally about half the blood is made of cells and half the blood is plasma. In relative polycythaemia there is a shortage of plasma, so that the red cells make up more than half the blood. There are not really too many red cells at all, but actually too little plasma! It is commonest in young men and may be associated with high blood pressure. Apparent, spurious or stress polycythaemia are other names for this condition.

Why does Polycythaemia occur ?

As explained, secondary polycythaemia is the result of a disorder elsewhere in the body. We do not know the cause for primary polycythaemia. Nor do we know the cause for relative polycythaemia, though heavy smoking and excessive alcohol consumption may play a role.

Treatment Involved for Polycythaemia

Treatment is needed in order to bring down the number of red cells in the blood. This will reduce the risk of complications such as blood clots. SECONDARY POLYCYTHAEMIA will improve by treating the underlying cause. If this is not possible, for example in the case of chronic chest disease, then blood may be removed. This is called venesection. Blood is collected from a vein in the arm. This is done in the same way as taking blood for a blood test but using a larger needle. A small local anaesthetic is given. The procedure is the same as when a blood donor gives blood. Venesection is performed as often as necessary to keep the red blood count down. This is usually every few weeks.

It is not possible to cure PRIMARY POLYCYTHAEMIA (PRV) is not amenable to cure, but the blood count can be controlled effectively in a number of ways. Venesection is often used to bring down the red blood cell count. This is usually done every few weeks depending on the blood count. Alternatively the activity of the bone marrow can be reduced by using chemotherapy drugs. These are the same sort of drugs that are used to treat cancer, but in this case they are used for their effect on the bone marrow. They are given as tablets, either daily or once every few weeks. The dose is adjusted according to the blood count. Only small doses are needed and there are no side-effects. Another way of reducing the activity of the marrow is by giving an injection of radioactive phosphorus ( P-32). This is painless and has no side-effects. It takes effect over a few weeks, so venesection or drugs may be needed as well until the P-32 has taken effect. The effect of one injection lasts a long time, usually for about a year. The choice between these different treatments will depend on several factors. These include age, the white blood cell and platelet count, and whether the spleen is enlarged. In most cases some form of treatment is needed longterm to keep the blood count under control.

RELATIVE POLYCYTHAEMIA would be most logically treated by increasing the amount of plasma in the body. However, there is no effective way of doing this. Stopping smoking and reducing alcohol intake may bring the blood count back to normal. If this is not effective then venesection may be required. This works because venesection removes both red cells and plasma, but the body replaces plasma faster than red cells!

During Treatment for Polycythaemia

Any symptoms should improve rapidly as the blood count comes under control. None of the treatments used produce significant side-effects. The blood count will be checked frequently no matter what treatment is being given. People sometimes worry about being given radioactivity (P-32). However, the amount of radiation given is actually very small.

If Polycythaemia is Left Untreated

One would be at risk of complications, especially blood clots in the legs (thrombosis) or strokes.

Effects on Family of Polycythaemia

None of the types of polycythaemia are inherited or infectious. The condition cannot be passed on to family or friends.