Chronic lymphocytic leukaemia (CLL) is a form of leukaemia in which there is an excess number of mature, but poorly functioning lymphocytes in the circulating blood. In CLL the major reason for the build-up of tumour cells is the failure of lymphocytes to die at the end of their normal life span. The rate of production of lymphocytes is not significantly increased and may even be lower than normal. Patients have enlarged but not tender lymph nodes and enlarged liver, or spleen, or both. About 15% of patients will either be anaemic (low haemoglobin levels) or have a low platelet count.
