Acute lymphoblastic leukaemia (ALL)

ALL is a fast-growing type of leukaemia (cancer of the blood) which affects lymphocyte white blood cells.

The cancer means you may not have enough healthy cells in your blood. This can cause problems with fighting infection, carrying oxygen and bleeding. 

There are 3 main types of blood cells:

• Red blood cells carry oxygen to all the tissues in your body.
• White blood cells are involved in fighting infection. 
• Platelets form clots which stop you from bleeding.

All blood cells come from cells known as stem cells. These start out as immature cells (blast cells) and then they develop into different types of mature blood cells.

• Lymphoid stem cells develop into lymphocytes. Lymphocytes are white blood cells that fight infection. They are further divided into T-cells and B-cells, depending on how they fight infection.
• Myeloid stem cells go on to form red blood cells, platelets and some types of white blood cells.

New blood cells are normally made in your bone marrow. Bone marrow is the soft spongy tissue that fills the centre of some of your bones. New cells move out of your bone marrow and into your blood. Old cells are replaced when needed. With leukaemia, this process of making and replacing blood cells goes wrong.

There are different types of ALL. For example: 

B-cell ALL

This affects B-cell lymphocytes. This is the most common type of ALL.

T-cell ALL

This affects T-cell lymphocytes.

Philadelphia-positive ALL

The Philadelphia chromosome is an abnormal chromosome sometimes found with ALL. It can help leukaemia cells to grow. 

The Philadelphia chromosome makes a protein that in turn causes an enzyme called tyrosine kinase to make more leukaemia cells in your bone marrow. If tests show that you have the Philadelphia chromosome, you can have a targeted therapy treatment that blocks the action of the tyrosine kinase enzyme. 

The cause of ALL is unknown. But there are certain things called risk factors that can increase your chance of developing the disease.

These include:          

• Exposure to chemicals: These include certain pesticides, benzene and other chemicals found in industry.
• Exposure to radiation: This includes exposure to high doses of radiation in industry or nuclear accidents or to previous radiotherapy.
• Genetic disorders: These include Down syndrome and Fanconi anaemia.
• Previous medical treatment: This includes taking previous chemotherapy or radiotherapy or drugs that affect your immune system.
• Being overweight.
• Being male.
• Cigarette smoking or exposure to cigarette smoke.
• Lowered immunity and some viral infections (HTLV-1).
• Age. ALL is more common in children, younger adult 15-25 and those over 70 years.

Medical content updated from our 'Understanding acute lymphoblastic leukaemia (ALL)' booklet (2024). Reviewed by Prof Mary Cahill, Consultant Haematologist and Chair of the ALL Clinical Advisory Group (ALL-CAG); Karena Maher, Haematology Advanced Nurse Practitioner; Fiona Young, Daffodil Centre Nurse; Mary O'Kelly, Daffodil Centre Nurse.