Leukemia - Description
Blood contains three types of cells: red blood cells, white blood cells, and platelets (pronounced PLATE-lits). Each type of cell has a special function in the body. Red blood cells carry oxygen from the lungs to the rest of the body. White blood cells fight invading organisms, such as bacteria and viruses. Platelets are involved in the process of blood clotting.
All blood cells form in the soft tissue that fills the center of bones. This tissue is called bone marrow. All three types of blood cells arise out of a primitive type of cell known as a stem cell. A stem cell can develop into a red blood cell, a white blood cell, or a platelet, depending on conditions.
Leukemia is caused by the overproduction of white blood cells. This has two effects on the body. First, the white blood cells may not mature properly as they develop. They may lack the ability to kill foreign bodies in the bloodstream. This defect seriously damages the immune system and the body loses its ability to fight off infections.
Second, so many white blood cells may form that they pack the bone marrow until there is not enough room for red blood cells and platelets to develop. Without red blood cells, the body's cells do not get enough oxygen, and the condition known as anemia (see anemias entry) develops. Anemia is characterized by general weakness, headache, pale skin, and dizziness. It can become a life-threatening disorder. Without platelets, blood cannot clot properly and simple injuries can lead to serious blood loss.
There are three types of white blood cells. Each has a special role to play in the immune system. The three types are granulocytes (pronounced GRAN-yuh-lo-site), lymphocytes (pronounced LIM-fuh-sites), and monocytes (pronounced MON-uh-sites). Leukemia may result in the overproduction of any one type of white blood cell. Each type of leukemia is named for two characteristics:
- Whether it is acute or chronic
- Whether it affects granulocytes, lymphocytes, or monocytes
- Acute:
- A condition that comes on fairly quickly.
- Bone marrow:
- Soft, spongy material found in the center of bones.
- Bone marrow biopsy:
- A procedure by which a sample of bone marrow is removed and studied under a microscope.
- Bone marrow transplantation:
- A procedure in which healthy bone marrow is injected into a leukemia patient's bones.
- Chronic:
- A condition that develops slowly and lasts a long time or is reoccuring.
- Immune system:
- A network of organs, tissues, cells, and chemicals designed to fight off foreign invaders, such as bacteria and viruses.
- Lumbar puncture:
- A procedure in which a thin needle is inserted into the space between vertebrae in the spine and a sample of cerebrospinal fluid is withdrawn for study under a microscope.
- Platelets:
- Blood cells that assist in the process of blood clotting.
- Red blood cells:
- Blood cells that carry oxygen from the lungs to the rest of the body.
- Stem cells:
- Immature blood cells formed in bone marrow.
- White blood cells:
- Blood cells that fight invading organisms, such as bacteria and viruses.
For example, one form of leukemia develops very slowly. It results in the overproduction of granulocytes. That form of leukemia is called chronic granulocytic leukemia. The same disease is also known by another name, chronic myelogenous (pronounced my-uh-LAJ-uh-nuhs) leukemia.
Another form of leukemia occurs rapidly. It results in the overproduction of lymphocytes. That form of leukemia is called acute lymphocytic leukemia.
Leukemias account for about 2 percent of all cancers. It is the most common form of cancer among children. For that reason, leukemia is sometimes called a disease of childhood. However, leukemias affect nine times as many adults as children. Half of all cases of the disease occur in people over sixty. The incidence of acute and chronic leukemias is about the same.
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