Understanding Leukemia - the Basics

What Is Leukemia?

Leukemia is an abnormal rise in the number of white blood cells. The white blood cells crowd out other blood cell elements such as red blood cells and platelets. The elevated white blood cells are immature and do not function properly.

Leukemia - the term derives from the Greek words for "white" and "blood" - is often considered a disease of children, yet it actually affects far more adults. It is more common in men than women and in Caucasians than African-Americans. There will be more than 52,000 new patients diagnosed with all forms of leukemia in the United States in 2014 with about 24,000 deaths.

Blood has three types of cells: white blood cells that fight infection, red blood cells that carry oxygen, and platelets that help blood to clot, all suspended in its liquid plasma. Every day, hundreds of billions of new blood cells are produced in the bone marrow - most of them red cells. In people with leukemia, however, the body starts producing more white cells than it needs. Many of the extra white cells do not mature normally, yet they tend to live well beyond their normal life span.

Despite their vast numbers, these leukemia cells are unable to fight infection the way normal white blood cells do. As they accumulate, they interfere with vital organ functions, including the production of healthy blood cells. Eventually, the body does not have enough red blood cells to supply oxygen, enough platelets to ensure proper clotting, or enough normal white blood cells to fight infection. This results in persons with leukemia being anemic as well as increasing their risks of bruising, bleeding, and infection.

Cases of leukemia are classified as acute or chronic. The cells in acute leukemia start multiplying before they develop beyond their immature stage. Chronic leukemia progress more slowly, with the leukemia cells developing to full maturity. Leukemia is further classified according to the type of white blood cell involved, most commonly myeloid or lymphoid. Under a microscope, the two main types of white blood cells are easily distinguishable as myeloid cells contain tiny particles or granules; lymphoid cells usually do not.

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.

Source: WebMD, LLC