Leukaemia

What is leukaemia?

Leukaemia is a type of blood cancer. It starts in the blood-forming tissue, usually the bone marrow, and leads to the over-production of abnormal white blood cells, the part of the immune system that defends the body against infection. 

To understand leukaemia, it helps to know more about your blood, which has three main cells groups. They have different jobs: 

• White blood cells fight off infection
• Red blood cells carry oxygen around your body, and take carbon dioxide back to your lungs so you can breathe it out
• Platelets helps your blood clot, to prevent bleeding

Your body is making fresh new blood cells all the time, to replace old ones that have worn out and died off. This happens mainly in your bone marrow. When you're healthy, this system is finely balanced in a process called haematopoiesis. 

• The process starts with a stem cell, which is an immature cell that can develop into all types of blood cells
• When the stem cell divides, it can either produce more stem cells or other immature blast cells that develop into mature blood cells over time 
• In this process of specialisation, immature blast cells become either lymphoid or myeloid cells 
• Lymphoid cells are a type of white blood cells. They help fight infection, and they include B lymphocytes and T lymphocytes
• Myeloid cells go on to form red blood cells, platelets and other types of white blood cells such as monocytes and granulocytes

Leukaemia develops when this process goes wrong, and the white blood cells develop in an uncontrolled way. Your body is making too many white blood cells and they may not be fully formed or mature. This means your white blood cells can't do their job of fighting infection. They may also crowd out your red blood cells and platelets, so they can't work properly either. 

Leukaemia symptoms may include:

• Unexplained weight loss
• Feeling tired or weak
• Easily bruise or bleed
• Swollen lymph nodes
• Swollen stomach
• Infections
• Fever/night sweats
• Pain in bones/joints

There are four main different types of leukaemia

The leukaemia name partly depends on whether it is chronic or acute:

• Chronic leukaemia may take a while to get worse
• Acute leukaemia gets worse quickly without treatment. The white blood cells are also more abnormal than in chronic leukaemia

The leukaemia name also tells you what specific type of white blood cell is affected, myeloid or lymphoblastic.

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Read more about the four main types of leukaemia: