An umbrella term for several malignant disorders of white blood cells, in which they proliferate in a disorganised manner. The disease is also characterised by enlargement of the SPLEEN, changes in the BONE MARROW, and by enlargement of the LYMPH glands all over the body. The condition may be either acute or chronic.
According to the type of cells that predominate, leukaemia may be classified as acute or chronic, and as lymphoblastic leukaemia or myeloid leukaemia. Acute lymphoblastic leukaemia (ALL) is mostly a disease of childhood and is rare after the age of 25. Acute myeloid leukaemia is most common in children and young adults, but may occur at any age. Chronic lymphatic leukaemia occurs at any age between 35 and 80, most commonly in the 60s, and is twice as common in men as in women. Chronic myeloid leukaemia is rare before the age of 25, and most common between the ages of 30 and 65; men and women are equally affected.
Both types of acute leukaemia seem to arise from a MUTATION in a single white cell. The genetically changed cell then goes through an uncontrolled succession of divisions resulting in many millions of abnormal white cells in the blood, bone marrow and other tissues. Possible causes are virus infection, chemical exposure, radiation and genetic background.
In acute cases the patient is pale due to anaemia, may have PURPURA due to lack of platelets, and have enlarged lymphatic glands and spleen. The temperature may be raised, so the condition can be mistaken for an acute infection (or may first become apparent because the patient develops a severe infection due to a lack of normal white blood cells).
In the chronic type of the disease the onset is gradual, and the first symptoms which occasion discomfort are either swelling of the abdomen and shortness of breath, due to painless enlargement of the spleen; or the enlargement of glands in the neck, armpits and elsewhere; or the pallor, palpitation, and other symptoms of anaemia which often accompany leukaemia. Occasional bleeding from the nose, stomach, gums or bowels may occur, and may be severe. Generally, there is a slight fever.
When the blood is examined microscopically, not only is there an enormous increase in the number of white cells, which may be multiplied 30- or 60-fold, but various immature forms are also found. In the lymphatic form of the disease, most white cells resemble lymphocytes, which, in healthy blood, are present only in small numbers. In the myeloid form, myelocytes, or large immature cells from the bone marrow, which are never present in healthy blood, appear in large numbers, and there may also be large numbers of immature, nucleated erythrocytes.
This varies according to the type of leukaemia and to the particular condition of the patient. In general, treatment is conducted over 2 years or more and consists of three phases: induction of remission (when there are no signs or symptoms of the disease); consolidating that remission; maintaining remission. Currently, treatment depends on using CHEMOTHERAPY as a combination of CYTOTOXIC drugs, based on a series of clinical trial results obtained systematically since the 1970s. In ALL, for example, induction may be with a VINCA ALKALOID such as vincristine, one of the ANTHRACYCLINES, ASPARAGINASE and a CORTICOSTEROID as well as blood and platelet transfusions as needed. During consolidation a different combination of chemotherapeutic agents may be used together with a BONE MARROW TRANSPLANT. Out-patient maintenance is generally with lower dose chemotherapy with drugs such as MERCAPTOPURINE and METHOTREXATE.
For the myeloid form, the principles of treatment are the same, although the initial remission rate is lower than in ALL and repeat induction may be required. AML which has reached the brain may be managed with cranial RADIOTHERAPY.
The prognosis varies with age and with the type of cell responsible for the malignant replication. The best prognosis is in those under 14 with ALL, in whom the 5-year survival rate is over 90%. The prospect is not so optimistic for older patients with AML.