Familial adenomatous polyposis 1

APC-associated polyposis conditions include: familial adenomatous polyposis (FAP), attenuated FAP, and gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS). FAP is a colon cancer predisposition syndrome in which hundreds to thousands of adenomatous colonic polyps develop, beginning, on average, at age 16 years (range 7-36 years). By age 35 years, 95% of individuals with FAP have polyps; without colectomy, colon cancer is inevitable. The mean age of colon cancer diagnosis in untreated individuals is 39 years (range 34-43 years). Extracolonic manifestations are variably present and include: polyps of the gastric fundus and duodenum, osteomas, dental anomalies, congenital hypertrophy of the retinal pigment epithelium (CHRPE), soft tissue tumors, desmoid tumors, and associated cancers. Attenuated FAP is characterized by multiple colonic polyps (average of 30), more proximally located polyps, and a diagnosis of colon cancer at a later age than in FAP. Certain extracolonic manifestations, such as gastric and duodenal polyps or cancers, are variably present in attenuated FAP; risk management may be substantially different between FAP and attenuated FAP. GAPPS is characterized by gastric fundic gland polyposis, increased risk of gastric cancer, and limited colonic involvement in most individuals reported.

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