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Learn more about Familial Adenomatous Polyposis (FAP)! Day 2 - Hereditary Cancer Awareness Week

Illustration by JR Bee, Verywell

Familial Adenomatous Polyposis (also known as FAP) is caused by mutations in the APC gene. The characteristic features of FAP are colorectal cancer and the development of hundreds of polyps throughout the colon and rectum. Individuals with FAP can develop colon polyps as early as the teen years, and if these polyps are not removed they will become cancerous.

Many people with FAP choose to remove their colon after the number of polyps becomes too numerous to manage by colonoscopy. The average age that colon cancer develops in FAP is 39, although the overall risk for colon cancer can be significantly reduced in individuals who have their colon removed.. There is also a milder form of the condition, called attenuated FAP, in which fewer polyps develop and at a later age. Attenuated FAP is also caused by mutations in APC. It is estimated that between 1 in 7,000 and 1 in 22,000 individuals have FAP. FAP is inherited in an autosomal dominant pattern, which means that only one mutated copy of a gene is necessary to increase the risk for polyps and cancer. Most of the time, the mutation is inherited from a parent. Up to 25% of FAP cases are due to new, or de novo, mutations. In these cases, the individual does not have a family history of FAP and the mutation is new in them. Browse the links below to learn more about familial adenomatous polyposis:

To find an inherited GI Cancer Genetics Clinic near you, check out the “Find a Clinic” page on the CGA-IGC website:

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