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 manag