What is acute myeloid leukaemia?

Acute myeloid leukaemia (AML) is also known as acute myelocytic, acute granulocytic or acute myelogenous leukaemia. In AML, abnormalities in blood cell production can cause symptoms such as anaemia, tiredness, excessive bleeding, unexplained bruising and susceptibility to infection. AML is more common in adults and is treated by chemotherapy, or a stem cell or bone marrow transplant.

What blood cells are affected?

AML 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.

Also see: Blood cell types

What are the symptoms of AML?

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, for example, 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.

Infections may be related to AML

Some people also experience infections as an initial symptom of AML and these can include skin boils or abscesses, tonsillitis, sinusitis or pneumonia. Occasionally, 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.

What causes AML?

The exact cause of AML is unknown but there are probably a series of minor events, which cumulatively lead to a break-down 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 treatment for a variety of conditions, have a slightly greater chance than others of developing leukaemia in later years.

People treated with chemotherapy and/or radiation treatment 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 in people.

How is AML diagnosed?

AML is usually identified by examining a blood sample, taken either at the hospital or a GP's surgery, under a microscope.

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.

Bone marrow sampling

Further analysis is often carried out using a sample of the person's bone marrow, which is tested using specialised laboratory techniques. This is in order to sub-classify the AML and provide information about the prognosis (long term outlook) and optimal choice of treatment. AML can be classified in to 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 5% of blast cells, but this may increase to 50-95% in AML.

What type of treatment is needed?

The initial treatment for a newly diagnosed patient with AML is chemotherapy or a stem cell or bone marrow transplant.

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.

Additional treatment

Following treatment, most patients generally recover and go on to display normal blood marrow appearances, achieving a complete remission. However, sometimes the disease can relapse (return) so patients are often given additional treatment to try to 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.

Related topics

See Leukaemia What does that term mean? See Cancer glossary

Also see the everybody Human Atlas video on Acute myeloid leukaemia

Original material provided by the Leukaemia and Blood Foundation of New Zealand, 2007. Edited by everybody, August 2010.