APC and Gardner syndrome: DF are usually present in familial adenomatous polyposis (FAP)-Gardner syndrome.(2,10) FAP is a hereditary cancer syndrome caused by the APC gene's germline mutation, which is transmitted in an autosomal dominant manner with nearly 100% penetrance.10The incidence ranges between 1:6,850 and 1:23,700 live births.11Affected people will develop hundreds to thousands of small adenomatous colonic polyps.