Familial adenomatous polyposis (FAP) is a rare inherited cancer predisposition syndrome characterized by hundreds to thousands of precancerous colorectal polyps (adenomatous polyps). If left untreated, affected individuals inevitably develop cancer of the colon and/or rectum. FAP is inherited in an autosomal dominant manner and caused by abnormalities (mutations) in the APC gene. Mutations in the APC gene cause a group of polyposis conditions that have overlapping features: familial adenomatous polyposis, Gardner syndrome, Turcot syndrome and attenuated FAP.
National Organization for Rare Disorders