According to Mayo Clinic, scientists do not understand exactly what causes leukemia, but they believe it stems from a combination of environmental and genetic factors. Changes that occur within cells that have yet to be understood by medical professionals or mutations that occur at the DNA level may contribute to leukemia.
Leukemia is a blood disease that causes an abnormal increase in white blood cells. According to WebMD, these white blood cells do not mature normally or function properly, but they can live way beyond a cell's normal lifespan. While they are great in number, the white blood cells that develop in someone with leukemia do not fight infections in the same manner as normal white blood cells. Instead, they interfere with the development of healthy blood cells and hinder the functions of the body's vital organs. Leukemia is a progressive disease, and as it develops, the red blood cells that supply oxygen to the body begin to diminish in number as do the platelets in the body that ensure proper blood clotting.
Leukemia affects children and adults, and it is more common in women than it is in men. The disease is also more common in Caucasians than African-Americans, notes WebMD.