The mean age of onset in APC-positive families was 46.3 years (range 35–56) for group 1 (attenuated FAP); 35.7 (range 18–67) for group 2 (intermediate FAP); and 29.2 (range 7–58) for group 3 (severe FAP). Here, APC is linked to Familial adenomatous polyposis.