Acute lymphoblastic leukaemia

What is ALL?

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

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.


People with ALL may experience a feeling of general weakness and lethargy, shortness of breath on exertion, signs of anaemia and possible 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.


The cause of ALL is largely unknown. It is likely that there are a number of factors rather than one single factor involved.

In rare cases, exposure to very large doses of radiation, or certain drugs used to treat other forms of cancer may increase the risk of ALL. Certain types of viral infections may play a role in the development of some types of ALL.


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

If ALL is present the 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 five per cent of blast cells. However, with ALL this can increase to 50-95 per cent.

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 and choice of treatment.


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.

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

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.

Please see our treatment section for more information on treatment for ALL.

Resources: Acute Lymphoblastic Leukaemia booklets

We have two detailed information booklets for ALL.

Acute Lymphoblastic Leukaemia in adults

Acute Lymphoblastic Leukaemia in children