Male patient with Anthony Nolan patient services staff member

Chronic lymphocytic leukaemia (CLL)

Chronic lymphocytic leukaemia (CLL) is a type of blood cancer that stops B lymphocytes (a type of white blood cell) from developing properly.

What is chronic lymphocytic leukaemia (CLL)?

Lymphocytes are involved in the working of your immune system.

Lymphocytes start life as lymphoblasts (immature lymphocytes). Having CLL means that lymphoblasts grow too quickly and don’t function properly. Over time, they gather in your lymphatic system and can cause large, swollen lymph nodes. They also fill up your bone marrow, preventing it from producing all types of healthy blood cells.

CLL is a chronic condition, which means it usually develops very slowly. Many people don’t need treatment for months or years. However, some people may need to have treatment straight away.

You can find out more about CLL, including symptoms, diagnosis and treatments, on the Leukaemia Care and Blood Cancer UK websites.

Facts about CLL

  • Nearly 4,000 people are diagnosed with CLL each year in the UK.
  • CLL is the most common type of leukaemia adults are diagnosed with in the UK.
  • CLL is more common in men, and people over the age of 70.
  • There were 17 stem cell transplants in the UK to treat CLL in 2022.

CLL and stem cell transplants

You will normally only be offered a stem cell transplant if your CLL hasn’t responded to initial treatment, or if your doctors think it’s unlikely to.

Most transplants for CLL are allogeneic transplants – when stem cells are donated to you by someone else.

Some people with CLL will have an autologous transplant – when doctors use your own stem cells – but this is very rare.

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Last updated: 04/04/2024
Next review due: 04/04/2025