Acute Myelocytic Leukemia Health Article

Definition

Acute myelocytic leukemia (AML) is an acute cancer that affects white blood cells, primarily those of the granulocyte or monocyte types.

Description

Acute myelogenous leukemia and acute nonlymphocytic leukemia (ANLL)are other names for AML and refer to the identical disease.

The cells that make up blood are produced in the bone marrow and the lymph system. The bone marrow is the spongy tissue found in the large bones of the body. The lymph system includes the spleen (an organ in the upper abdomen), the thymus (a small organ beneath the breastbone), and the tonsils (an organ in the throat). In addition, the lymph vessels (tiny tubes that branch like blood vessels into all parts of the body) and lymph nodes (pea-shaped organs that are found along the network of lymph vessels) are also part of the lymph system. The lymph is a milky fluid that contains cells. Clusters of lymph nodes are found in the neck, underarm, pelvis, abdomen, and chest.

The main types of cells found in the blood are the red blood cells (RBCs), which carry oxygen and other materials to all tissues of the body; white blood cells (WBCs), which fight infection; and the platelets, which play a part in the clotting of the blood. The white blood cells can be further subdivided into three main types: granulocytes, monocytes, and lymphocytes.

The granulocytes, as their name suggests, have particles (granules) inside them. These granules contain special proteins (enzymes) and several other substances that can break down chemicals and destroy microorganisms such as bacteria. Monocytes are the second type of white blood cell. They are also important in defending the body against pathogens. The lymphocytes form the third type of white blood cell.

The bone marrow makes stem cells, which are the precursors of the different blood cells. These stem cells mature through stages into either RBCs, WBCs, or platelets. In acute leukemias, the maturation process of the white blood cells is interrupted. The immature cells (or "blasts") proliferate rapidly and begin to accumulate in various organs and tissues, thereby affecting their normal function. This uncontrolled proliferation of the immature cells in the bone marrow affects the production of the normal red blood cells and platelets as well.

Acute leukemias are of two types: acute lymphocytic leukemia and acute myelogenous leukemia. Different types of white blood cells are involved in the two leukemias. In acute lymphocytic leukemia (ALL), it is the lymphocytes that become cancerous. AML is a cancer of the monocytes and/or granulocytes.

The reason certain leukemias are now called acute is because of names received decades ago. Before the discovery of modern methods of cancer treatment, these were illnesses that progressed rapidly. In contrast, chronic leukemias were, in this period before newer methods had been invented, illnesses that progressed more slowly.

Demographics

Approximately 23 new cases of AML appear per each million Americans each year. Men are somewhat more likely to develop AML than are women. Approximately 29 new cases appear per every million males while approximately 19 new cases appear per every million females per year.

Older persons are considerably more likely to develop AML. Approximately 13 people per million younger than 65 years of age will develop AML. In contrast, 122 people per million older than 65 years of age will develop the disease.

AML sometimes affects children. About 500 children develop AML in the United States every year. Approximately one in five of all children who develop leukemia develop AML. The disease affects boys and girls in roughly equal numbers. Children of all ethnic groups may develop the disease. If one of two identical twins develops AML, the chances are considerable that the other twin will develop it as well.