Acute lymphoblastic leukaemia (ALL) is a blood cancer that appears suddenly and grows quickly. It starts when immature white blood cells called blasts become cancerous. These abnormal blast cells are known as leukaemia cells. They multiply quickly and continue to divide but never mature into normal cells.
Because the leukaemia cells are immature and abnormal, they don’t carry out the usual infection-fighting role of white blood cells. They also crowd out normal white blood cells, which then can’t work properly. This increases the risk of infections. When the bone marrow fills with leukaemia cells, there is little room for normal red blood cells and platelets. This can cause fatigue, bleeding problems and other health issues.
Learn more about:
- The difference between acute and chronic leukaemia
- The difference between ALL and AML
- How leukaemia starts
- What causes ALL
- Who gets ALL
- The blood
- The lymphatic system
What is the difference between acute and chronic leukaemia?
While all types of leukaemia start in the bone marrow and affect white blood cell production, they are grouped according to which type of white blood cell is affected, whether there are abnormalities in the bone marrow, and how quickly the disease develops.
Acute leukaemia usually affects undeveloped cells, occurs suddenly and grows quickly. Chronic leukaemia usually affects partly developed cells, appears gradually and grows slowly over months to years. For more on this see Chronic leukaemia – CLL or Chronic leukaemia CML.
There are two types of acute leukaemia:
- acute lymphoblastic leukaemia (ALL)
- acute myeloid leukaemia (AML).
What is the difference between ALL and AML?
ALL and AML are the two main types of acute leukaemia. The difference between them is the type of white blood cell affected.
Acute lymphoblastic leukaemia (ALL) – ALL can develop from different types of lymphocytes, including B-cells or T-cells. See more on how ALL is diagnosed and treated.
Acute myeloid leukaemia (AML) – Develops from myeloid cells. There are different subtypes of AML, including a subtype known as acute promyelocytic leukaemia (APML) that develops from immature myeloid cells called promyelocytes. APML is treated differently.
How leukaemia starts
The bone marrow produces three main types of blood cells: white cells, red cells and platelets. Leukaemia starts when abnormal white blood cells become cancerous and crowd the bone marrow before moving into the bloodstream. Without treatment, they can spread to lymph nodes and some organs.
Children with acute leukaemia
This information is for adults diagnosed with acute leukaemia. As children and adults with acute leukaemia have similar types of tests, treatments and side effects, much of the information here will also apply to children. No two cases of acute leukaemia are the same, so it is important to discuss your child’s case in detail with their doctors. Learn more about children with acute leukaemia.
What causes ALL?
The exact causes of acute leukaemia are not yet understood. Things known to increase the chance of developing the disease include:
- previous treatment with chemotherapy or radiation therapy
- having certain genetic disorders, such as Down syndrome
- exposure to high levels of radiation (e.g. nuclear accident)
- exposure to some chemicals, such as benzene
- smoking
- obesity
- particular blood disorders, such as myelodysplasia (for AML)
- some viruses, such as Epstein-Barr virus (for ALL).
Who gets ALL?
Each year in Australia, more than 3700 people are diagnosed with a form of leukaemia, and it is the most common type of cancer diagnosed in people under 24. About 1400 of these cases are acute leukaemia, accounting for about 1.1% of cancer cases in Australia, so overall, acute leukaemia is rare.
About 370 people are diagnosed with acute lymphoblastic leukaemia (ALL) each year. Of these, more than 200 are children under 15. ALL mostly occurs in children 1–4 years old.
The blood
Blood is pumped around your body to provide oxygen and nutrients to your tissues, and to remove waste products. It is made up of blood cells carried in a clear fluid called plasma.
All blood cells live for a limited time and need to be continually replaced. Most are made in the bone marrow, which is the spongy part in the centre of the bones.
Bone marrow contains blood stem cells. These are unspecialised cells that usually grow into one of the three main types of blood cells: red blood cells, white blood cells or platelets. Each type of blood cell has a specific job to do.
There are two families of blood stem cells:
- lymphoid stem cells – develop into white blood cells called lymphocytes, which are an important part of the immune system
- myeloid stem cells – develop into red blood cells, platelets, and all white cells apart from lymphocytes.
When lymphoid white blood cells grow abnormally this is called acute lymphoblastic leukaemia and when myeloid white blood cells grow abnormally this is called acute myeloid leukaemia.
What is the lymphatic system?
The lymphatic system is part of the immune system, which protects the body against disease and infection. It is a network of vessels, tissues and organs.
Lymph vessels – These thin tubes are found throughout the body. They carry lymph fluid.
Lymph fluid – This clear fluid travels to and from the tissues in the body, carrying nutrients and taking away bacteria, viruses, abnormal cells and cell debris.
Lymph nodes – These are small structures in the neck, underarms, chest, abdomen and groin. They filter toxins, help fight infections, and produce some blood cells.
Spleen – This is an organ in the abdomen. It clears out old or damaged blood cells.
More resources
A/Prof John Moore (Conjoint UNSW), Senior Staff Specialist Haematology, Department of Haematology and Bone Marrow Transplant, Kinghorn Cancer Centre, St Vincent’s Hospital; Glynda Blomson, Consumer; Kevin Bloom, Senior Social Worker, Haematology and Bone Marrow Transplant, Royal North Shore Hospital; Sharon Frazer, Consumer; Prof Angela Hong, Radiation Oncologist, Chris O’Brien Lifehouse, and Clinical Professor, The University of Sydney; Yvonne King, 13 11 20 Consultant, Cancer Council NSW; Karen Maddock, Clinical Nurse Consultant – Haematology, Westmead Hospital.
View the Cancer Council NSW editorial policy.
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