Acute Myelogenous Leukemia
(AML)

Alternative names: Myeloid Leukemia, Acute Myelocytic Leukemia, Acute Granulocytic Leukemia, and Acute Non-lymphocytic Leukemia.

AML is a cancer that starts in cells that would normally develop into different types of blood cells.  Most cases of AML develop from cells that would turn into white blood cells (other than lymphocytes), but some cases of AML develop in other types of blood-forming cells.  There are different types of AML.  AML starts in the bone marrow, but in most cases it quickly moves into the blood.  It can sometimes spread to other parts of the body including the lymph nodes, liver, spleen, central nervous system (brain and spinal cord), and testicles in males.  "Acute" means that the leukemia can progress quickly, and if not treated, would probably be fatal in a few months.

AML results from acquired (not inherited) genetic damage to the DNA of developing cells in the bone marrow.  The effects are: 1) the uncontrolled, exaggerated growth and accumulation of cells called "leukemic blasts" which fail to function as normal blood cells and 2) the blockade of the production of normal marrow cells, leading to a deficiency of red cells (anemia), and platelets (thrombocytopenia) and normal white cells (especially neutrophils, i.e. neutropenia) in the blood.

Incidence; Causes and Development; Contributing Risk Factors

About 10,600 new cases of acute myelogenous leukemia are diagnosed each year in the United States.  Some 15% of childhood leukemia cases are of acute myelogenous leukemia.

AML is not contagious and is not inherited.  AML can occur in a variety of ways; different types of cells may be seen by the physician in blood or marrow.  Since most patients have one of seven different patterns of blood cell involvement, these patterns have formed a subclassification.  Myeloblasts are undeveloped cells.  If they are the dominant leukemic cells in the marrow at the time of diagnosis the leukemia is referred to as "myeloblastic" type.  If there are many myeloblasts but there are some cells developing towards fully formed blood cells, the added designation "with maturation" is used.  If there are cells that are developing features of monocytes ("monocytic" type) or red cells ("erythroleukemic"), these designations are used and so forth.

Even though the leukemia cells look somewhat like blood cells, the process of their formation is incomplete.  Normal, healthy blood cells are insufficient in quantity.

In most cases the cause of AML is not evident.  Several factors have been associated with an increased risk of disease.  These include:

• Exposure to high doses of irradiation, as carefully studied in the Japanese survivors of atomic bomb detonations
• Exposure to the chemical benzene, usually in the work place
• Exposure to chemotherapy used to treat cancers such as breast cancer, cancer of the ovary or the lymphomas.

Uncommon genetic disorders such as Fanconi anemia, Down syndrome and others are associated with an increased risk of AML.  Older people are more likely to develop the disease.  AML incidence increase dramatically among people who are over the age of 40.  They are most prevalent in the sixth, seventh and eighth decades of life.

Signs and Symptoms

Most patients feel a loss of well-being.  They tire more easily and may feel short of breath when physically active.  They may have a pale complexion from anemia.  Several signs of bleeding caused by a very low platelet count may be noticed.  They include black-and-blue marks or bruises occurring for no reason or because of a minor injury, the appearance of pin-head sized spots under the skin, called petechiae, or prolonged bleeding from minor cuts.  Mild fever, swollen gums, frequent minor infections like pustules or perianal sores, slow healing of cuts or discomfort in bones or joints may occur.

Diagnosis and Tests

To diagnose the disease the blood and marrow cells must be examined.  In addition to low red cell and platelet counts, examination of the stained (dyed) blood cells with a light microscope will usually show the presence of leukemic blast cells.  This is confirmed by examination of the marrow, which invariably shows leukemic blast cells.  The blood and/or marrow cells are also used for studies of the number and shape of chromosomes (cytogenetic examination), immunophenotyping and other special studies, if required.

Treatment and Prevention

The subclassification of the disease is important.  Different types of therapy may be used and the likely course of the disease may be different.  Additional features may be important in guiding the choice of therapy, including: abnormalities of chromosomes, the cell immunophenotype, the age and the general health of the patient, and others.