Acute lymphoblastic leukaemia (ALL)

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 (myeloid or lymphoid), whether there are abnormalities in the bone marrow, and how quickly the disease develops.

Acute leukaemia – This usually affects fully immature cells, occurs suddenly, and develops quickly. There are two types of acute leukaemia: acute lymphoblastic leukaemia (ALL) and acute myeloid leukaemia (AML).

Chronic leukaemia – This usually affects partly immature cells, appears gradually, and develops slowly over months to years. There are two types of chronic leukaemia: chronic lymphocytic leukaemia (CLL) and chronic myeloid leukaemia (CML).

Each year in Australia, more than 3200 adults and 250 children are diagnosed with a form of leukaemia, and about 1311 of these cases are acute leukaemia. Overall, acute leukaemia is rare, accounting for about 1.1% of all cancer cases in Australia.

• Over 300 people are diagnosed with ALL each year.
• Of these 180 are children under 15.
• ALL usually occurs in children 1–4 years old. 

The exact causes of acute leukaemia are not yet understood, but some factors may increase the chance of developing the illness, including:

• previous treatment with chemotherapy or radiation therapy
• having certain genetic disorders such as Down syndrome
• viral infections
• cigarette smoking
• exposure to high levels of radiation (such as an atomic bomb explosion)
• exposure to some chemicals, such as benzene, petroleum products, paints, certain pesticides and heavy metals, over a long period of time.

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 red blood cells, white blood cells and platelets, all carried in a clear fluid called plasma. 

All three types of blood cells have a limited life span and need to be continually replaced. Most are made in the bone marrow, which is the spongy part in the centre of the bones.

The bone marrow contains stem cells. These are unspecialised blood cells that first develop into immature cells known as blast cells. Normally, the blast cells then become mature red or white blood cells or platelets and carry out their set functions.

There are two families of stem cells:

• myeloid stem cells – develop into myeloblast cells and then into red blood cells, most types of white blood cells, and platelets
• lymphoid stem cells – develop into lymphoblast cells and then into lymphocytes, which are a type of white blood cell.

If myeloblast or lymphoblast cells do not mature properly or if there are too many in the blood, it can cause leukaemia.

The lymphatic system

The lymphatic system works with the white blood cells to protect the body against infection. A large network of thin tubes (lymph vessels) carries a clear fluid called lymph.

The lymph travels to and from areas of lymph tissue, including the lymph nodes, spleen and liver. When leukaemia causes abnormal white blood cells to build up, the lymph tissue becomes swollen.

Lymph nodes – Also known as lymph glands, these are small bean-shaped structures that are found in the neck, underarms, chest, abdomen and groin. The lymph nodes filter out toxins and help fight infections, and also produce some blood cells.

Spleen – An organ on the left side of the body under the ribs. It filters out old or damaged blood cells, and also makes some blood cells.

Liver – The body’s largest internal organ. It removes toxins, stabilises sugar levels, and stores vitamins.