Leukemia

Although we divide diseases into “genetic” and “infectious” categories, many diseases are influenced by a combination of factors. These diseases are harder to classify and treat than diseases that are caused by one determining factor. Many researchers have studied leukemia, but the underlying cause of the disease has not been conclusively demonstrated. Leukemia is not caused by a disease organism and is not infectious. It is a genetic disease, in that it is caused by malfunctioning genes, but it is acquired rather than inherited, with the exception of CML. It is caused by an injury to the genes of bone marrow cells. This injury, which makes the cells function incorrectly, also gives them a competitive advantage over normal cells, allowing them to multiply and replace normal cells.

This genetic damage seems to have a variety of causes. Risk factors may lie in a person's genetic inheritance. People with Down's syndrome and certain other genetic disorders are also more likely to get leukemia. In some cases, leukemia seems to run in families. This may be due to an inherited susceptibility to gene abnormalities. In addition, population studies have shown that unlike other cancers, immigrant groups retain the leukemia risk of their countries of origin rather than their new environments, suggesting an important genetic role in the disease.

More often, leukemia is caused by a person's exposure to a substance in their environment. Environmental risk factors affecting adults include “exposure to radiation, benzene, pesticides, cigarette smoke, and extremely low-frequency electromagnetic fields” (Robien and Ulrich, 2003). Each of these environmental factors induces genetic mutation, which can lead to leukemia. However, in most cases of leukemia, none of these risk factors are present. Leukemia often develops in people with no family history of the disease or significant exposure to any of the environmental risk factors.