Understanding Leukemia -- the Basics
What Causes Leukemia?
No one knows exactly what causes leukemia. Certain chromosome abnormalities have been associated with leukemia, but they do not cause it. For example, virtually all people with chronic myeloid leukemia (CML) and some with acute lymphocytic leukemia (ALL) have an abnormal chromosome known as the Philadelphia Chromosome in their white blood cells and bone marrow. As with other leukemia types, the chromosome abnormality is an acquired abnormality; it is neither inherited nor passed on to one's children.
Genetic disorders associated with acute myeloid leukemia (AML) include Down syndrome, Bloom syndrome, Fanconi anemia, or immune deficiency disorders such as Wiskott-Aldrich syndrome and ataxia-telangectasia. In addition, at least one virus in the same family as the human immunodeficiency virus (HIV) has been associated with a rare form of the disease -- the HTLV-1 virus.
Environmental factors also seem to influence the risk of developing leukemia. Tobacco smokers are more prone to certain leukemias. Research also suggests that prolonged exposure to radiation, various chemicals in home and work environments -- such as petroleum products -- and non-ionizing radiation is associated with leukemia.
Leukemia is also a rare complication of chemotherapy and radiation therapy used to treat other cancers. The risk of leukemia depends upon the types of chemotherapy drugs used. The risk of developing acute leukemia is greatest in persons who have received both chemotherapy and radiation. This factor is most commonly associated with prior treatment for breast cancer, Hodgkin's lymphoma, and non-Hodgkin's lymphoma. Other prior cancers associated with the development of acute leukemia are myeloma, testicular cancer, and sarcoma.
Ionizing radiation such as from nuclear explosion exposure, uranium and uranium dust exposure, and radon is associated with the development of leukemia.
Family history is a risk factor for leukemia as well. For example, if an identical twin develops ALL there is a 20% chance the other twin will develop it within a year. After a year, the risk then falls off to the same risk as non-identical twins, but still remains five times that of the general population.