Acute leukaemia is classified according to the type of white blood cells affected by cancer. There are two main types:

• lymphocytes, which are mostly used to fight viral infections
• neutrophils, which perform several functions, such as fighting bacterial infections, defending the body against parasites and preventing the spread of tissue damage

These pages focus on acute lymphoblastic leukaemia, which is cancer of the lymphocytes. The following other types of leukaemia are covered elsewhere:

• chronic lymphocytic leukaemia
• chronic myeloid leukaemia
• acute myeloid leukaemia

Warning signs of acute leukaemia

Symptoms of acute lymphoblastic leukaemia usually begin slowly before rapidly getting severe as the number of immature white blood cells in your blood increases (see below for an explanation of this). Symptoms include:

Read more about the symptoms of acute lymphoblastic leukaemia.

What happens in acute leukaemia

All of the blood cells in the body are produced by bone marrow – a spongy material found inside bones.

Bone marrow produces specialised cells called stem cells which have the ability to develop into three important types of blood cells:

• red blood cells, which carry oxygen around the body
• white blood cells, which help fight infection
• platelets, which help stop bleeding

Usually the bone marrow produces stem cells which are allowed to fully develop before being released into the blood. But in acute leukaemia, bone marrow starts releasing large numbers of immature white blood cells known as blast cells.

As the number of blast cells increases there is a drop in the number of red blood cells and platelet cells. This drop causes the symptoms of anaemia, such as tiredness, and increases the risk of excessive bleeding.

Also, blast cells are less effective than mature white blood cells at fighting bacteria and viruses, making you more vulnerable to infection.

How common is acute lymphoblastic leukaemia?

Around 8,600 people are diagnosed with leukaemia each year in the UK. In 2011, 654 people were diagnosed with acute lymphoblastic leukaemia.

Despite being uncommon overall, acute lymphoblastic leukaemia is the most common type of cancer to affect children. Approximately one in every 2,000 children will develop it. About 85% of cases occur in children aged under 15, mostly between the ages of two and five years old.

The cause or causes of acute leukaemia are uncertain, but known risk factors include:

• exposure to high levels of radiation
• exposure to benzene, a chemical used in manufacturing that is also found in cigarettes

Read more information about the causes of acute lymphoblastic leukaemia.

Outlook

The outlook for children with acute lymphoblastic leukaemia is usually good. Almost all children will achieve a remission (a period of time where they are free from symptoms) from their symptoms, and 85% will be completely cured.

The outlook for adults with acute lymphoblastic leukaemia is less promising as only 40% of people with the condition will be completely cured.

Treatments for acute lymphoblastic leukaemia usually involve a combination of chemotherapy and radiotherapy. In some cases, a bone marrow transplant may also be needed to achieve a cure.

Read more about the treatment of acute lymphoblastic leukaemia.

If a cure is not possible, there is a risk that the lack of healthy blood cells can make the person extremely vulnerable to life-threatening infections (due to the lack of white blood cells) or uncontrolled and serious bleeding (due to the lack of platelets).