Familial adenomatous polyposis syndrome
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.
Familial adenomatous polyposis syndrome affects 1 in 10,000 births . The average age of presentation is 16 years.
- colorectal carcinoma (see below)
- hepatoblastoma (400-fold increased risk compared to general population )
- extracolonic polyps (stomach, duodenum)
- desmoid tumors
- dental anomalies
- congenital hypertrophy of the retinal pigment epithelium
- papillary thyroid carcinoma - usually cribriform morular variant
Typical symptoms and signs include rectal bleeding, diarrhea, abdominal pain, anemia, and/or mucosal discharge . Polyps usually develop around puberty .
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 .
MUTYH gene has been associated with APC-negative FAPS; this has an autosomal recessive inheritance and this is often called MUTYH-associated polyposis (MAP).
There are three variants of FAPS:
- Gardner syndrome
- attenuated familial adenomatous polyposis
- familial polyposis coli
Familial adenomatous polyposis syndrome has a varied imaging appearance and demonstrate innumerable polyps. Imaging usually underestimates the number of polyps because most are <5 mm in size. Features of colorectal carcinoma (CRC) should also be actively sought out.
Treatment and prognosis
Familial adenomatous polyposis syndrome 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 .
Total colectomy with ileoanal anastomosis is generally considered the surgical treatment of choice .
Other polyposis syndromes should be considered :
- Cronkhite-Canada syndrome
- Peutz-Jeghers syndrome
- Cowden syndrome (multiple hamartoma syndrome)
- juvenile polyposis syndrome