Acute myeloid leukemia (AML) is a type of leukemia—a cancer of the bone marrow and blood. This disease is sometimes referred to as acute myelogenous leukemia or acute myelocytic leukemia.
The American Cancer Society estimates that about 20,800 people are diagnosed with AML each year in the U.S. AML is the most common type of acute leukemia—more common than acute lymphoblastic leukemia—in adults. The majority of people diagnosed are 65 years old or older.
What Is AML?
In people with AML, some blood stem cells begin to function abnormally, producing immature myeloid cells (also called blasts) that transform into cancer. Unlike normal blasts, the leukemic blasts don’t mature into red blood cells, white blood cells, or platelets, and they interfere with the ability of normal blasts to mature as well. This increases the number of blasts and reduces the number of normal mature blood cells in the body. Also, unlike normal blasts, leukemic blasts can escape from the bone marrow to the bloodstream and be transported to other parts of the body, such as the skin, lungs, or brain, where they can grow and interfere with the normal functions of these organs. The reduction in normal blood cells and the growth of leukemic blasts in other areas of the body are usually what cause AML symptoms.
AML progresses quickly and may lead to serious infections and organ failure if it is not treated. Since these complications make the disease more difficult to treat, it is important to start treatment fairly soon after diagnosis. In order to optimize treatment, in some cases it may be best to wait for results of diagnostic tests that provide details about the classification of your disease before starting treatment.
Understanding the Bone Marrow and Blood
To understand leukemia, it helps to have basic knowledge of the bone marrow and how healthy blood cells form and what they do.
Stem cells are cells in the body that have the potential to turn into any kind of cell, such as a skin cell, a liver cell, a brain cell, or a blood cell. Stem cells that turn into blood cells are called hematopoietic stem cells, or blood stem cells. Blood stem cells are mainly found in bone marrow (the soft, spongy tissue inside your bones), but some are also found in circulating blood. Normal blasts (immature blood cells) are found only in the bone marrow, not in circulating blood. When blood cells become old or damaged, they die, and blood stem cells produce new blood cells to replace them.
Blood stem cells produce myeloid stem cells and lymphoid stem cells. Myeloid stem cells produce myeloblasts, which turn into white blood cells, known as granulocytes, as well as red blood cells and platelets. Lymphoid stem cells produce lymphoblasts, which in turn produce several types of white blood cells, including lymphocytes and natural killer cells.
- White blood cells (leukocytes) fight infection.
- Red blood cells (erythrocytes) carry oxygen from the lungs to the other parts of the body and take carbon dioxide back to the lungs to be removed.
- Platelets (thrombocytes) make the blood clot and slow or stop bleeding.
What Causes AML?
Doctors do not know what causes AML. The disease typically affects older people—the average age of a patient with AML is 66 years. It is also slightly more common in males than females. Often changes or mutations in specific genes or chromosomes are seen in people with AML.
The few known risk factors that may increase your odds for developing AML include:
- Being exposed to certain chemicals, such as chemotherapy or benzene
- Being exposed to high levels of radiation
- Having certain blood disorders, such as myeloproliferative disorders or myelodysplastic syndromes
- Having certain genetic conditions, such as Down syndrome
- Having a family history of AML, such as having a parent or sibling with AML, especially an identical twin who had AML as an infant or young child
Keep in mind that most people who develop AML have none of the risk factors and most people with the risk factors do not develop the disease.