Familial adenomatous polyposis (FAP) is caused by a mutation in the APC gene. FAP is usually inherited, but sometimes happens to individuals with no family history of the disorder. Approximately one percent of colon cancer is caused by FAP.
What does FAP do?
Most people are at risk of developing a polyp here and there, usually starting around age 50. But people with FAP develop hundreds of polyps, usually starting in their teenage years. Having so many polyps (polyposis) gives people with FAP a 100% chance of developing colon cancer, usually by age 45.
How is FAP treated?
People with FAP who follow conventional treatment only have one option: surgery. A way to prevent so many polyps from forming hasn't been proven yet, so the safest thing is to remove the colon and rectum. This doesn't necessarily result in the use of a colostomy bag since procedures such as the j-pouch operation can connect the small intestine to a man-made pouch that serves as a rectum and allows normal bowel function.
To learn more about how genes can influence cancer risk, please read Genetics and Colorectal Cancer Risk.
Familial Adenomatous Polyposis (FAP). Mount Sanai Hospital. 1 Sep. 2006 [http://www.mtsinai.on.ca/familialgicancer/Diseases/FAP/treatment.htm].