What is leukaemia

The term ‘leukaemia’ actually describes a group of cancers involving an excess of white blood cells.

In leukaemia, normal control mechanisms in the blood break down and the bone marrow starts to produce large numbers of abnormal white blood cells, disrupting production of normal blood cells and affecting the vital functions that these blood cells carry out.

Leukaemia can be classified as either lymphoid or myeloid, denoting the type of white blood cell affected. It is also categorised as either acute or chronic, reflecting the speed of progression.

Acute leukaemias

Almost all childhood leukaemias are of the acute form, meaning that they progress rapidly.

• Acute lymphoblastic (lymphoid) leukaemia (ALL) accounts for more than 80% of cases of childhood leukaemia. It is the only form of leukaemia – and one of the few forms of cancer – that is more common in children than in adults.

• Acute myeloid leukaemia (AML) accounts for most of the remaining cases.

Chronic leukaemias

Chronic leukaemias, which progress slowly, are very rare in childhood.

• Chronic myeloid leukaemia (CML) accounts for less than 3% of childhood leukaemias (less than 15 children per year in the UK).

• Chronic lymphoblastic leukaemia is unheard of in children.