What is acute lymphoblastic leukaemia?

Acute lymphoblastic leukaemia (ALL) is a blood-related disease involving abnormal blood cell production, and mostly occurs in children. Treatments include chemotherapy and stem cell or bone marrow transplant, and possibly radiation treatment.

What goes wrong?

ALL is caused by the abnormal division of bone marrow stem cells, which damage the controlling genes of the cells, and lead to a reduction in the number of normal blood cells. These immature cells, usually referred to as blast cells, do not function properly.

Also see: Blood cell types

Children affected

ALL is the most common type of leukaemia in children. It also occurs in adolescents and adults, but with less frequency. The disease can appear suddenly and progress rapidly.

What are the symptoms of ALL?

People with ALL may show a variety of symptoms, including a shortage of red blood cells, a feeling of general weakness and lethargy, shortness of breath on exertion, signs of anaemia and possibly swollen ankles.

Children may have severe pain in their bones or joints of their arms, legs or both.

People may also have a problem with bleeding, such as unexplained bruises, spontaneous nosebleeds or excessive bleeding after minor injury.

Some infections can also be an initial symptom, including skin boils, abscesses, tonsillitis, sinusitis or pneumonia. Occasionally such infections result in fever for which no specific cause can be found.

What causes ALL?

The cause of the cell damage is largely unknown. There is some evidence to suggest that children of mothers x-rayed during pregnancy, or children who received radiation therapy for other conditions have an increased risk of developing ALL in later life.

As ALL is predominantly a disease that occurs in children, it is possible that it could be due to an abnormal response of the bone marrow to a common infectious agent such as a virus. However, to date no virus or any other infectious agent has been identified.

As the cases tend to be random, there is also no suggestion that the disease is inherited.

How is ALL diagnosed?

If ALL is suspected, a blood sample is normally taken either at the hospital or at a GP's surgery, and examined under the microscope.

In ALL, the blood sample will show the presence, sometimes in great quantities, of blast cells (immature cells). Further examination of the bone marrow will show excessive numbers of blast cells, usually resembling those already identified in the blood.

Normal bone marrow contains around 5% of blast cells. However, with ALL this can increase to 50-95%.

Once the diagnosis is made, blood and marrow cells are examined further, using a number of specialised laboratory techniques to sub-classify the ALL and provide information about the prognosis (long term outlook) and choice of treatment.

What treatment is needed?

The two main treatments for ALL are - chemotherapy and a stem cell or bone marrow transplant. In some instances radiation therapy may also be used.

Without treatment, the bone marrow will produce increasing numbers of abnormal cells and the production of normal blood cells will fail almost completely.

A sharp reduction in the number of red cells in the blood causes anaemia, and the shortage of normal white cells and platelets becomes more severe.

Remission is treatment goal

The aim of treatment is for people to go into complete remission, with normal blood and bone marrow.

With treatment, approximately 90% of patients recover, go into complete remission, and show normal blood and bone marrow. However, relapses can occur, where cell abnormalities start to re-develop in the cells.

Related topics

See Leukaemia 

What does that term mean? See Cancer glossary

Original material provided by the Leukaemia and Blood Foundation of New Zealand, 2007. Edited by everybody, September 2010.