Familial adenomatous polyposis syndrome

Dr Henry Knipe et al.

Familial adenomatous polyposis syndrome (FAPS) is characterised 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 FAPS is used to described the entire spectrum.

FAPS affects 1 in 10,000 births 1,3. The average age of presentation is 16 years.

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

FAP is characterised 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.

Genetics

FAPS results from mutation of the tumour supressor 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 FAPS; this has an autosomal recessive inheritance 6 and this is often called MUTYH-associated polyposis (MAP).

Associations
Variants

There are three variants of FAPS:

  • Gardner syndrome
  • attenuated familial adenomatous polyposis
  • familial polyposis coli

FAPS has a varied imaging appearance and demonstrate innumberable polyps. Imaging usually underestimates the number of polyps because most are <5mm in size. Features of colorectal carcinoma (CRC) should also be actively sought out.

FAPS accounts for 0.5% of CRC cases with ~7% of FAP carriers developing CRC by age 21 with almost every carrier developing CRC by 35-40 years 1,2.

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

Other polyposis syndromes should be considered 6:

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Article Information

rID: 32801
Sections: Pathology, Syndromes
Synonyms or Alternate Spellings:
  • Familial adenopolyposis (FAP)
  • Familial adenomatous polyposis (FAP)
  • Familial adenomatous polyposis
  • Colorectal adenomatous polyposis
  • MUTYH-associated polyposis (MAP)
  • Familial adenomatous polyposis syndrome (FAPS)
  • Familial polyposis coli syndrome (FAP)
  • Familial polyposis coli syndrome

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