Overview

The leukaemias are a group of cancers of the blood forming tissues that are typically characterized by the type of white blood cells that is affected (lymphoid or myeloid) and the progressive nature of the abnormal cells (acute versus chronic). There are four common types of leukaemia: (i) acute lymphocytic leukaemia (ALL); (ii) chronic lymphocytic leukaemia (CLL); (iii) acute myeloid leukaemia (AML); and (iv) chronic myeloid leukaemia (CML). Specifically, ALL is defined as an abnormal white blood cell count and differential, abnormal haematocrit/haemoglobin and platelet counts, abnormal bone marrow with more than 5% blasts (immature cells), and signs and symptoms of the disease (http://cancer.gov). ALL and AML occur in both children and adults, although the chronic leukaemias (CLL, CML) affect primarily adults. Approximately 89% of leukaemia cases occur in adults over the age of 60 years (Lesko, 1998). The incidence of leukaemia in the United States is 10.9 per 100 000 individuals compared to 8.5 per 100 000 individuals in the United Kingdom (Parkin et al., 1997).

The specific aetiology of leukaemia is unknown, although risk factors may consist of prenatal exposure to radiation and postnatal exposure to various toxins (see ‘Toxins: environmental’). Treatments typically used in the management of specific neoplasms often place individuals at secondary risk for other malignancies including leukaemia. Down's syndrome and other genetic disorders, such as neurofibromatosis also pose significant risk factors for the development of leukaemia (NIH Publication number 02-3775 retrieved from http://cancer.gov).