Leukaemia

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Leukaemia is the name for a number of cancers of the white blood cells. White blood cells are the cells that fight infection in the body.

Blood cells are produced in the bone marrow, the spongy tissue that forms the centre of the bone. In leukaemia, white blood cells multiply in an uncontrolled and abnormal way. They gradually take the place of the other parts that normally make up the blood. There is little room in the bone marrow for the other types of blood cells and for new blood cells to be produced. This can cause a shortage of red blood cells (anaemia), severe bleeding (because normal blood clotting doesnâ€™t happen) or serious infection (as a result of weakened immune system).

There are different types of leukaemia, depending on what type of white blood cell is involved, and how it is affected.The two main groups are:

Chronic leukaemias, in which those affected may live with symptoms for years. In chronic lymphocytic leukaemia (CLL) there is an increase in the number of a type of white blood cells called lymphocytes. In chronic myeloid leukaemia (CML) there is overproduction of another type of white blood cell called myeloids or granulocytes. These cells are abnormal, so are not able to carry out the normal functions of white blood cells, such as fighting infection. They also live too long, so over a period of time they replace the fully-functioning cells (white, red and platelets) in the bone marrow. This is a slow process and tends to get worse over time.
Acute leukaemias, which are more aggressive and develop quickly. Acute lymphoblastic leukaemia (ALL) is overproduction of immature (underdeveloped) lymphocytes, called lymphoblasts. Acute myeloid leukaemia (AML) is overproduction of immature myeloid white blood cells. In acute leukaemias, the cells reproduce very rapidly, and so do not become mature enough to carry out their jobs in the immune system. This is a quicker process than in chronic leukaemias.

Leukaemia forms only around 2% of cancers diagnosed in the UK each year. In 2000, there were 6,800 new cases (Cancer Research UK). Leukaemia is the most common cancer in children, causing around one third of childhood cancers, but there are far more cases in adults.

The most common childhood leukaemia is acute lymphoblastic leukaemia (ALL) but the most common leukaemia overall is chronic lymphocytic leukaemia (CLL).