familial adenomatous polyposis

Last edited 08/2019 and last reviewed 09/2021

Familial polyposis coli is characterized by the presence of 100 to more than 1000 tubular adenomas which carpet the colon. Less frequently, lesions occur in the stomach and the small bowel, particularly the duodenum.

This condition has a prevalence of 1 in 7000 to 1 in 24000, and is most commonly inherited in an autosomal dominant fashion, although one-third of cases are sporadic. The adenomatous polyposis gene (APC gene) is located on the long arm of chromosome 5

• individuals with a family history (several close relatives affected) of early-onset colon cancer with multiple polyps may have familial polyposis coli (familial adenomatous polyposis) and can be offered testing for the APC gene (this can be identified in the majority of cases of classical familial polyposis coli) (1)
• management involves endoscopic surveillance of at-risk individuals from their early teens - colectomy once polyposis has been established (1)

The polyps usually appear in the second and third decade and have 100% malignant potential. Bleeding usually heralds malignant change and a poor prognosis.

Extra-gastrointestinal lesions may occur in variants.

Reference:

1. Pulse (2005); 65(14):55-60.
2. Groden J (1995). Colon-cancer genes and brain tumours. NEJM; 332: 884-5.
3. Hodgson, SV. et al. (1994). Genetic heterogeneity of congenital hypertrophy of the retinal pigment epithelium (CHRPE) in families with familial adenomatous polyposis. J. Med. Genet.;31(1): 55-8.