Genomics and Disease

What's the Problem?

Most human diseases result from the interaction between genetic factors and modifiable environmental factors such as chemical exposures, and behavioral factors like diet and lifestyle. The field of genomics studies a person's complete set of genes—known as the genome—and their functions, including interactions with environmental and behavioral factors. (Genetics is the study of single genes and their influence on human life and disease progression.) Genomics can provide new insights into why some people, but not others, get sick from certain infections, environmental exposures, and behaviors. To date, many diseases have been shown to have a key genetic component including: cancer, heart disease, Alzheimer's disease, cystic fibrosis, diabetes, schizophrenia, sickle cell anemia, Down syndrome and alcoholism. As scientists learn more about the different genetic variations that exist, the role that genes play in disease, death and disability will be better understood.

Who's at Risk?

Everyone is potentially at risk for disease, but risk among individuals is unique and varies depending on a person's genes, their lifestyle choices and environmental exposures. Taking a family history is one way to assess a person's risk for disease as it allows them to explore how disease has impacted their family. This assessment takes into account not only those factors which may have been inherited, such as genes that are linked to disease, but also shared environmental factors, culture and behaviors.

Can It Be Prevented?

Even though a person cannot change their genetic makeup, knowing their family history can help reduce the risk of developing health problems. Compiling a family history is an important tool that can capture the interactions of genes, the environment and lifestyle conditions in relation to a person's risk for disease. Information about one's family history can help physicians assess their patient's risk of developing common diseases and may influence early detection. When an inherited risk is suspected based on family history, a physician will consider other risk factors and may recommend screening tests, such as mammograms or blood cholesterol, or lifestyle changes. Genetic testing may also be recommended for selected chronic diseases such as breast cancer and cardiovascular disease. It is also used for rare-single gene disorders, such as sickle cell anemia or Huntington's Disease. Because various genes involved in chronic disease have yet to be determined, family history remains a low-cost tool to identify those at risk.

The Bottom Line

• Genetics plays an important role in the development of many chronic diseases.
• Differences in risk of developing disease exist among individuals based on their inherited susceptibilities, environmental exposures and behavioral factors.
• Family history is one of the best, low-cost genomic tools available today.

Case Examples

1. Linda, a 55-year-old attorney, is battling Huntington's disease. A degenerative condition that is always fatal and usually only diagnosed in people in middle age, Huntington's is an inherited disease. Linda encourages her daughter Andrea to take the test to see if she carries the gene for the disease. Initially opposed to the idea, Andrea visits a genetic counselor who explains the benefits and drawbacks of taking the test. After much consideration, Andrea decides to take the test so she can be informed about whether she will develop the disease and can plan her future accordingly.
2. Howard and Jeanine, an African American couple in their early 30's, are considering having a child. Howard knows he is a carrier for sickle cell anemia, an inherited blood disorder that affects 1 in 70,000 to 80,000 individuals in the United States. African Americans, in particular, are at an increased risk for the disease as it occurs in approximately 1 in 500 African American newborns. Together, they decide that Jeanine will get tested for the sickle cell linked gene. As a result of testing, they are able to have the information they need in order to make an informed decision about having children.
3. At a recent visit to his physician, Robert, a 38-year-old insurance salesmen, receives troubling news. Robert has high cholesterol and high blood pressure—both of which are risk factors for heart disease. Robert knows that his father, aunt and cousin have had heart disease. His physician explains that although heart disease has a genetic component that can be inherited, it is the interactions between genes and environmental and lifestyle factors that determine if one will develop the disease. Robert decides to reform his lifestyle by eating a healthier diet, exercising more often and avoiding bars and restaurants that allow smoking.