Leukaemia is a general term for a group of malignant disorders that are characterized by the presence of an abnormally large number of leucocytes in the blood and bone marrow. The disorder may be acute or chronic, and there are various types named according to the kind of leucocyte involved. Unlike ordinary leucocytes, leukaemic cells have the ability to reproduce themselves.

The most common form is acute lymphoblastic leukaemia. As its name implies, it affects lymphocytes, the white blood cells formed mainly in the lymph nodes and bone marrow. It usually occurs in children. In the bone marrwow, leukaemic cells replace the normal ones, with the result that red cells, platelets and normal leucocytes cannot be produced and become reduced in number. This results in anaemia (lack of red cells), thrombocytopenia (lack of platelets, with the attendant risk of haemorrhage because the blood will not form clots) and leucopenia (lack of normal white cells). This latter condition makes the patient particularly susceptible to infection.

Treatment with corticosteroid and cytotoxic drugs often brings about remissions in the disorder. Similar methods are use to treat acute myeloblasts leukemia, in which the cells that normally produce polymorphonuclear leucocytes are afflected. It usually occurs in middle age. The on-going form of leukaemia that affects polymorph cells is known as chronic myeloid leukaemia, with onset generally after the age of 35. Often the liver and spleen are enlarged, with loss of appetite and fatigue. A combination of drug treatment and radiotherapy is often prescribed.

Chronic lymphatic leukaemia may also involve swelling of the liver, spleen and lymph nods. There is an over-abundance of lymphocytes in the blood. The usual victims are men more than 50 years old. Treatment is similar to that for chronic myeloid leukaemia, sometimes with the addition of blood transfusions. Although leukaemia is not a single disorder but a group of related disorders, because of its prevalence it continues to be the subject of active worldwide research. Again, no single cause has been found. Genetic factors (such as the presence of Down’s syndrome), a history of virus infection in the patient’s mother during pregnancy, and exposure to ionizing radiation have all been correlated with a slight increase in incidence of leukaemia.