Familial adenomatous polyposis syndrome

Last revised by Samira Jahan on 02 Dec 2022

Familial adenomatous polyposis syndrome (FAPS) is characterized by the presence of hundreds of adenomatous polyps in the colon. It is the most common of the polyposis syndromes.

Familial polyposis coli, attenuated familial adenomatous polyposis and Gardner syndrome are all variants of the same disease and familial adenomatous polyposis syndrome is used to describe the entire spectrum.

Familial adenomatous polyposis syndrome affects 1 in 10,000 people 1,3. The average age of presentation is 16 years.

Typical symptoms and signs include rectal bleeding, diarrhea, abdominal pain, anemia, and/or mucosal discharge 4. Polyps usually develop around puberty 5.

Familial adenomatous polyposis syndrome is characterized by the presence of hundreds or thousands of colonic adenomatous polyps, usually tubular or tubulovillous. The rectum is occasionally spared. Less commonly they affect the small bowel and stomach.

Familial adenomatous polyposis syndrome results from mutation of the tumor suppressor adenomatous polyposis coli (APC) gene located on chromosome 5q21-2. Around one-third of cases are thought to be sporadic (i.e. no family history) and two-thirds thought to be familial 1.

MUTYH gene has been associated with APC-negative familial adenomatous polyposis syndrome; this has an autosomal recessive inheritance 6 and this is often called MUTYH-associated polyposis (MAP).

There are three variants of familial adenomatous polyposis syndrome:

  • Gardner syndrome

  • attenuated familial adenomatous polyposis

  • familial polyposis coli

Familial adenomatous polyposis syndrome has a varied imaging appearance and demonstrates innumerable polyps. Imaging usually underestimates the number of polyps because most are <5 mm in size. Features of colorectal cancer should also be actively sought out.

Familial adenomatous polyposis syndrome accounts for 0.5% of colorectal cancer cases with ~7% of FAP carriers developing colorectal cancer by age 21, and almost every carrier developing colorectal cancer(CRC) by 35-40 years 1,2.

Total colectomy or proctocolectomy with ileoanal anastomosis is generally considered the surgical treatment of choice 5.

Other polyposis syndromes should be considered 6:

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Cases and figures

  • Case 1
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  • Case 2: infiltrative desmoid tumor
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