About chronic lymphocytic leukaemia (CLL)

What is leukaemia?

Leukaemia is cancer of your white blood cells and bone marrow. Bone marrow is the place where blood cells are made in your body. With leukaemia, immature blood cells divide quickly and do not grow into mature cells. These immature cells crowd your bone marrow and prevent it from making normal healthy cells.

Bone marrow

Bone marrow is the spongy material that fills your bones. It makes all the different types of blood cells in your body and replaces them when they grow old. The earliest cells are called stem cells and bone marrow is rich in them. Stem cells grow and develop into red blood cells, white blood cells and platelets.

• Red blood cells carry oxygen to all the tissues in your body.
• White blood cells fight infection.
• Platelets help your blood to clot if you cut yourself.

Once these cells are mature, they leave your bone marrow and enter your bloodstream. Normally the cells are made and replaced in a controlled way as needed. White blood cells have a short life span and only live for a few days.

Types of leukaemia

Leukaemia can be divided into two main groups depending on how fast the disease develops. Acute leukaemia develops quickly, whereas chronic leukaemia develops more slowly. The word ‘acute’ does not refer to how successful the treatment will be.

The type of leukaemia also depends on which kind of white blood cell is affected. There are many different types of white blood cells. These include myeloid and lymphoid cells. Myeloid cells develop into red blood cells, white blood cells and platelets. Lymphoid cells develop into white blood cells called lymphocytes. As a result, there are four main types of leukaemia:

• Acute lymphoblastic leukaemia (ALL)
• Acute myeloid leukaemia (AML)
• Chronic lymphocytic leukaemia (CLL)
• Chronic myeloid leukaemia (CML)

Lymphocytes fight infection in different ways in your body. They are further divided into T cells and B cells, depending on how they fight infection.

What is chronic lymphoblastic leukaemia (CLL)?

Chronic lymphoblastic leukaemia (CLL) is a slow-growing cancer of the lymphoid cells called lymphocytes. These immature lymphocyte cells are called blast cells. The blast cells are overproduced and crowd your bone marrow, preventing it from making healthy blood cells needed by your body. If your white cells cannot work properly, it leads to an increased risk of infection.

How common is CLL?

CLL is the most common leukaemia in the western world. About 109 people were diagnosed with it in Ireland in 2009.

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