About leukaemia

Diagram of how blood cells develop from stem cells

What is leukaemia?

Leukaemia is a cancer that affects white blood cells. To understand leukaemia it helps to understand a bit about how blood cells are made.

Blood cells

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 help your blood to clot.

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

  • Lymphoid stem cells develop into lymphocytes. These white blood cells 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 other types of white 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.

Diagram of how blood cells develop from stem cells

About leukaemia

Leukaemia is caused when your bone marrow makes too many white cells. Other cells such as red blood cells or platelets can be affected as well. Sometimes leukaemia is called blood cancer.

When leukaemia develops, immature blood cells (stem cells) continue to grow quickly but do not mature into white blood cells. These immature cells do not enter your blood stream. Instead, they fill up your bone marrow and prevent normal blood cells from growing there. You get sick because there aren’t enough healthy blood cells to do their jobs in the body. 

Types of leukaemia

There are four main types of leukaemia:

Their names come from the type of cell affected by the leukaemia (myeloid blast cells or lymphoid blast cells) and from how quickly they develop (chronic or acute).

Chronic leukaemia

The disease develops slowly, usually over months or years.

Acute leukaemia

The leukaemia develops quickly, over days and weeks.

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