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Chronic lymphocytic leukaemia (CLL)

Chronic lymphocytic leukaemia (CLL) is a specific type of leukaemia which affects the B lymphocytes (a type of white blood cell). It is a slowly progressing leukaemia.

Blood cells are formed in the bone marrow, which is the spongy tissue found inside bones. Blood-forming stem cells divide to produce either more stem cells or immature cells that become mature blood cells over time. A blood stem cell may become a myeloid stem cell or a lymphoid stem cell. In CLL it affects the lymphoid stem cells.

A lymphoid stem cell becomes a lymphoblast cell and then one of three types of lymphocytes (white blood cells):

In CLL the bone marrow produces too many B lymphocytes which are not fully developed (immature). These cells fill up the bone marrow, preventing it from producing normal, healthy cells. 

CLL progresses slowly but, although it can be treated, it is not usually possible to cure chronic leukaemia with standard treatments.

  • Published: Aug 2016
  • Next planned review: Aug 2018