Causes
For most people with leukemia, there's no way to identify what causes it. In some cases, though, specific risk factors can be identified:
- chemotherapy
- exposure to high doses of radiation or to benzene (found in unleaded gasoline, tobacco smoke, the chemical industry)
- family history
- genetic abnormality
- genetic disorders, such as Down syndrome and Fanconi anemia
All forms of cancer that can spread within the body (malignant), including leukemia, are thought to be due to genetic abnormalities (mutations). In leukemia, the damage occurs in the bone marrow stem cells. These special cells help to manufacture all the other cells in the blood. With this condition the production of these cells is out of control. Most people with one type of leukemia (CML, described below), have an abnormality in chromosome 22, called the Philadelphia chromosome.
Different Types of Leukemia
Acute leukemia develops rapidly, and large numbers of immature cells - called "blasts" - build up. These cells can't function as well as normal white blood cells so these people at higher risk of infection. Because the body is so busy producing "blasts," it can't make as many red blood cells or platelets which can cause anemia and bleeding disorders.
Chronic leukemia, which progresses more slowly than the acute form, involves overproduction of mature white blood cells that cannot function like normal white blood cells.
The four types of leukemia are:
- Acute lymphocytic leukemia (ALL) - the most common form in children - has uncontrolled production and buildup of immature white blood cells. The high numbers interfere with the production of red blood cells as well.
- Chronic lymphocytic leukemia (CLL) almost always occurs in people over 50 years of age. It is the most common type of leukemia overall, and occurs about twice as often in men as in women. It develops at a slower rate than ALL. Gradually, leukemic cells outnumber the normal-functioning cells in certain tissues in the body, including the bone marrow where other blood cells are made.
- Acute myeloid leukemia (AML) causes uncontrolled production and buildup of cells called myeloblasts. This interferes with the levels of functioning red blood cells, platelets, and normal white blood cells. AML is the most common form of acute leukemia in adults.
- Chronic myelogenous leukemia (CML) occurs more slowly than AML and has less effect on the development of other cell types. Chances of getting CML are one in one million for children under 10 and 1 in 10,000 for people over 80.