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Familial Adenomatous Polyposis (FAP) is a well-characterized autosomal dominant hereditary colorectal cancer syndrome. It is defined by the development of hundreds to thousands of colorectal adenomatous polyps, typically starting in adolescence, with a near-100% risk of Colorectal cancer (CRC) by age 40 if left untreated.

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“Colon Cancer That Runs in Families” (Familial Adenomatous Polyposis), APC Gene, Symptoms, Treatment

Etiopathogenesis

Genetics and Pathophysiology:

https://doi.org/10.3389/fonc.2021.570241

APC gene is a tumor suppressor that regulates β-catenin and Wnt signaling. Loss of APC function leads to uncontrolled epithelial proliferation and adenoma formation.

• Gene: APC (Adenomatous Polyposis Coli)
• Chromosome: 5q21
• Mutation type: Germline loss-of-function mutation
• Inheritance: Autosomal dominant
• Penetrance: High (but expressivity can vary)

Clinical Features

A. Colonic Manifestations

• >100 adenomatous polyps in the colon and rectum by the second or third decade
• Typically detected via colonoscopy
• Colorectal carcinoma inevitable if colectomy is not performed

B. Extracolonic Manifestations