Colon Polyps: The Link to Inherited Gene Mutations

At 38, Mark prided himself on a healthy lifestyle. He exercised regularly, ate a low-fat diet, kept stress to a minimum and maintained a weight of 170 pounds on his 6-foot frame. Since he took pains to make sure he'd stay healthy, he was taken aback to learn that he had several colon polyps, one of which turned out to be malignant. He was even more surprised that doctors traced the cause to an inherited gene mutation.

What Are Colon Polyps?

A colon polyp is a small growth located on the inner lining of the large intestine. It might be either harmless or of a type that can progress to cancer, the American College of Gastroenterology states.

Colon polyps can look either raised or flat. Some even grow on stalks like mushrooms. While the majority of these polyps don't turn into cancer, most cases of colon cancer are the result of colon polyps. This is the third leading cancer in the United States. It's also the second leading cause of death related to cancer.

Doctors identify and remove most colon polyps during a colonoscopy, then send them to a laboratory for analysis. When multiple growths are present, they're sometimes scattered throughout the individual's colon.

The most common causes of colon polyps are age, smoking, obesity, alcohol intake, a high-fat diet, consuming red meat and eating little fiber. However, an additional risk factor for developing colon polyps is gene mutations.

The Genetic Factor

According to the Mayo Clinic, gene mutations are responsible for certain types of colon cancer. Doctors classify some of these mutations as autosomal dominant. This means that children only need to inherit one defective gene from either parent to have an elevated risk. However, not every person with a mutated gene develops the type or types of cancer associated with it. Genetic testing can now identify a propensity to develop many colon polyps resulting from inherited mutations.

The most common colon disorders linked to genetics include:

Familial adenomatous polyposis (FAP). This rare condition causes the development of up to thousands of polyps in the lining of the large intestine while the patient is a teen. In individuals who don't undergo treatment, the risk of colon cancer is almost 100 percent, often before they reach 40 years old.

Gardner's syndrome. It's a variant of FAP. It causes polyps to arise throughout both the colon and the small intestine. Some patients also develop benign tumors in their skin, bone and abdomen.

MYH-associated polyposis (MAP). The disorder resembles FAP in some ways. Patients typically have more than one adenomatous polyp and can develop colon cancer as young as their twenties.

Lynch syndrome. It's the most common form on genetically based colon cancer. Doctors also sometimes refer to it as hereditary nonpolyposis colorectal cancer (HNPCC). While affected individuals usually develop few polyps in the colon, the ones that grow there typically become malignant very fast. These patients often experience additional tumors in areas such as the breast, small intestine, ovary, stomach and urinary tract.

Peutz-Jeghers syndrome (PJS). While the initial polyps are benign, some turn into colon cancer. The earliest sign of this condition is often freckles that appear all over the individual, including the lips, gums and feet.

When an individual has even the possibility of a genetic link to colon cancer, the treating general practitioner or internist refers the patient to a gastroenterologist and, in some cases, a specialist in genetics. Anyone with a family history of the inherited conditions causing polyps that can lead to cancer should at least consider receiving genetic counseling. Doctors recommend removing a patient's entire colon for some conditions. However, regular monitoring for colon polyps linked to genetics is sufficient for many patients.

Sources:

http://www.acg.gi.org/patients/gihealth/colonpolyps.asp

http://www.mayoclinic.com/health/colon-polyps/DS00511