What is chronic lymphocytic leukaemia?

Chronic lymphocytic leukaemia (CLL) is the most common type of leukaemia. It is more common in older people. About 3,200 people in the UK are diagnosed with it each year. CLL usually develops very slowly which is why it’s called a chronic leukaemia. Acute leukaemias develop more quickly.

Many people with CLL don’t need treatment for months or years. However, if people have symptoms, they may need treatment sooner.

CLL is a cancer of the white blood cells which develop from the lymphoid stem cells. In people with CLL, the bone marrow makes too many abnormal white blood cells called lymphocytes. When these cells are examined under a microscope, they look normal. But they aren’t fully developed (immature) and don’t work properly.

Over time, these abnormal lymphocytes build up in the lymphatic system and may cause large, swollen lymph nodes. The abnormal lymphocytes can also build up in the bone marrow. This leaves less space for normal white blood cells, red blood cells and platelets to develop.

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Signs and symptoms of CLL

Symptoms of CLL can include tiredness, repeated infections or a swelling in the neck, armpit or groin. Find out more.