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.

Terminology

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

Epidemiology

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

Associations

• colorectal carcinoma (see below)

• hepatoblastoma (400-fold increased risk compared to the general population ³)

• extracolonic polyps (gastric adenoma, gastric hamartoma, duodenal adenoma)

• desmoid tumors

• epidermal cyst (facial) ⁹

• osteomas (skull and mandible)

• dental anomalies

• congenital hypertrophy of the retinal pigment epithelium

• papillary thyroid carcinoma - usually cribriform-morular variant ⁸

• juvenile nasopharyngeal angiofibroma (rarely, in male patients) ^10-12

Clinical presentation

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

Pathology

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.

Genetics

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 are 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).

Variants

There are several variants of familial adenomatous polyposis syndrome:

• Gardner syndrome

• Turcot syndrome

• attenuated familial adenomatous polyposis

• familial polyposis coli

Radiographic features

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.

Treatment and prognosis

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

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

Differential diagnosis

Other polyposis syndromes should be considered ⁶:

• Cronkhite-Canada syndrome

• Peutz-Jeghers syndrome

• Cowden syndrome (multiple hamartoma syndrome)

• juvenile polyposis syndrome