Acute myeloid leukaemia (AML)
What is AML?
Acute myeloid leukaemia (AML) is also known as acute myelocytic, acute granulocytic or acute myelogenous leukaemia. It can occur in children and adolescents but is more common in adults and affects the myeloid line of cells, which consists of four types of blood cells - granulocytes, monocytes, red blood cells and platelets.
AML occurs when immature, or baby myeloid, cells start developing at a rapid rate, reducing the number of mature cells. If too many young cells accumulate in the blood they can cause blockages of the blood vessels.
People with AML may show a variety of symptoms including anaemia, a feeling of general weakness and lethargy, shortness of breath on exertion, a feeling that the heart is pounding, or possibly swollen ankles. They may also have problems with bleeding, e.g. unexplained bruises, excessive bleeding after a minor injury or surgery, or women may experience unusually heavy menstrual periods.
Bleeding gums or the presence of blood in the urine or after a bowel motion, can also be signs that the disease is present but are also common of many other, less serious conditions. Some people also experience infections as an initial symptom and these can include skin boils or abscesses, tonsillitis, sinusitis or pneumonia. Occassionally, such infections result in fever where there appears to be no specific cause.
It is quite common for a person to be diagnosed with AML having previously shown no symptoms.
Acute promyelocytic leukaemia (APML) is part of the same family as AML but it behaves slightly differently. APML is characterised by a switching of two chromosomes within the DNA.
Causes
The exact cause of AML is unknown but there are probably a series of minor events, which cumulatively lead to a breakdown in cell programming.
People exposed to excessive doses of irradiation, such as survivors of the nuclear bombs at Hiroshima and Nagasaki in Japan in 1945, and patients who have received radiation therapy for a variety of conditions, have a slightly greater chance of developing leukaemia in later years.
People treated with chemotherapy and/or radiotherapy for previous cancers may in later years develop a 'secondary' leukaemia, which could be due to the action of these drugs on the developing blood cells in the bone marrow.
There is no strong evidence to suggest that any other chemicals, viruses or infectious agents cause AML.
Diagnosis
AML is usually identified by examining under a microscope a blood sample, taken either at the hospital or a GP's surgery.
If AML is present, the sample will show evidence of immature myeloid cells, usually referred to as blast cells. In a healthy person these cells are normally only found in the bone marrow, and then in very small quantities. Further analysis is often carried out using a sample of the person's bone marrow, which is tested using specialised laboratory techniques to sub classify the AML and provide information about the prognosis and optimal choice of treatment. AML can be classified into one of seven sub-types.
Examination of the bone marrow will show excessive numbers of blast cells, reflecting those already identified in the blood. Normal bone marrow contains less than five per cent of blast cells, but this may increase to 50 - 95 per cent in AML.
Treatment
Without treatment, the bone marrow produces greater quantities of abnormal cells and eventually the production of normal blood cells fails almost completely.
A sharp reduction in the number of red cells in the blood causes anaemia and the shortage of normal white cells and platelets becomes more severe.
The initial treatment for a newly-diagnosed patient with AML is chemotherapy, or a stem cell or bone marrow transplant.
Following treatment, most patients generally recover and go on to display normal blood marrow appearances, achieving a complete remission. However, sometimes the disease can reoccur (relapse) so patients are often given additional treatment to try and reduce the risk of this and turn remission into a complete cure. These subsequent doses of chemotherapy are referred to as 'consolidation' or 'intensification' chemotherapy and are aimed at stopping the return of the disease.
For more information about this disease, or a copy of our information booklet on AML, please contact lbf@leukaemia.org.nz or call 0800 15 10 15.
