Familial Adenomatous Polyposis

About

Most people inherit the genetic defect that causes FAP from a parent who carries the mutation. But in about 25 percent of cases, the defect occurs spontaneously at conception. The majority of affected people begin to develop polyps in their teenage years, and many undergo prophylactic colectomy — surgical removal of the colon to prevent cancer — in their early 20s. People who have a spontaneous mutation aren't usually screened and may not know they have FAP until they develop symptoms of colorectal cancer.

Patients with FAP are at risk of other cancers, especially of the duodenum — the first part of the small intestine — of noncancerous tumors, and of dental and eye abnormalities. Careful monitoring for these and other complications is an essential part of caring for children and adults with FAP.

Some people develop a variant form of FAP called attenuated adenomatous polyposis. It, too, results from mutations in the APC gene, but causes fewer polyps and a later onset of cancer. People with attenuated adenomatous polyposis are at increased risk of cancer in the upper digestive tract, but are less likely to experience other complications common to FAP.