Acute lymphoblastic leukaemia and the blood

Leukaemia is a cancer of the blood. Most types of leukaemia cause the bone marrow to make abnormal white blood cells. These cells can get into the blood stream and circulate around the body. They do not work normally and so do not give you the protection from infection that they should.

Because there are far too many of these abnormal white blood cells, they can build up in the lymph nodes, bone marrow and spleen and cause swelling. They can also sometimes build up in the liver, the brain or the spinal cord and make them work less well.

There are several types and subtypes of leukaemia. The name of the leukaemia you have depends on

• How quickly it develops
• The type of white blood cells it affects

Acute lymphoblastic leukaemia (ALL) affects the white blood cells called lymphocytes. It usually develops quickly over days or weeks. It is the most common type of leukaemia to affect children but can also affect adults.

Doctors divide leukaemia into two main groups - acute and chronic. Acute leukaemia develops very quickly. Chronic leukaemia tends to develop slowly, usually over months or years without causing many symptoms.

Doctors divide these groups further, depending on the type of white blood cell they affect.

In acute leukaemia,

• Acute myeloid leukaemia (AML) affects myeloid cells
• Acute lymphoblastic leukaemia (ALL) affects lymphoid cells

In chronic leukaemia

• Chronic myeloid leukaemia (CML) affects myeloid cells
• Chronic lymphocytic leukaemia (CLL) affects lymphoid cells

This section is about acute lymphoblastic leukaemia (ALL). There is information elsewhere on CancerHelp UK about other types of leukaemia. The links above take you to information about the other types. Or you can look for them on our list of cancer types.

To understand how and why leukaemia affects you as it does, it helps to know how you make blood cells.

Your body makes blood cells in the bone marrow. The bone marrow is the soft inner part of your bones. You make blood cells in a controlled way, as your body needs them.

All blood cells start as the same type of cell, called a stem cell. This stem cell then develops into

• Myeloid stem cells – which become white blood cells called monocytes and neutrophils
• Lymphoid stem cells – which become white blood cells called lymphocytes
• Erythroblasts – which become red blood cells
• Megakaryocytes – which become platelets

The diagram below helps to explain this.

There is more about blood cells and what they do in the section about your body on CancerHelp UK.

In acute lymphoblastic leukaemia, the bone marrow makes too many lymphocytes. These lymphocytes are not fully developed and are not able to work normally.

White blood cells help fight infection. But if your body makes abnormal white blood cells, they don’t work properly. So you are more likely to get infections and find it difficult to get rid of them.

Too many white blood cells can overcrowd the bone marrow. So, there is not enough space for other types of blood cells. Then you may have a lower than normal count of red blood cells and platelets.

Having too few red blood cells makes you tired and breathless (anaemic). And if you don’t have enough platelets, you can have bleeding problems (for example, nosebleeds).

Abnormal white blood cells can build up in parts of the lymphatic system, such as the spleen and lymph nodes, making them swell. They may build up in the liver. This can make your tummy (abdomen) swell and feel uncomfortable. The leukaemia cells can also spread to the brain, and the testicles in men.

There is detailed information about the symptoms of acute lymphoblastic leukaemia in this section of CancerHelp UK

Lymphomas are another type of cancer that can develop from the white blood cells called lymphocytes. The main difference is that ALL starts in the bone marrow and may spread to other parts of the body. But lymphomas start in the lymph nodes and other organs, and then may spread into the bone marrow.

If you have cancerous lymphocytes in both your bone marrow and lymphatic system, it can sometimes be difficult to tell whether you have ALL or lymphoma. Your tests help your doctor to diagnose which it is. You can find more information about non Hodgkin’s lymphoma and Hodgkin’s lymphoma in the sections on different types of cancer.