Familial adenomatous polyposis
Familial adenomatous polyposis (FAP) is an inherited syndrome characterised by the development of hundreds to thousands of polyps in the large bowel, a process that begins in childhood. Cancerous transformation of one of these many polyps is almost universal and left untreated, this condition invariably progresses to colorectal cancer. Its contribution to the overall incidence of colorectal cancer is small (<1%), but diagnosis allows close monitoring of the affected individual and, through genetic testing, their close relatives as well.
As the mode of inheritance is autosomally dominant, possession of a mutant allele from a single parent is enough to produce the syndrome described above. FAP is caused by a germline mutation of a tumour suppressor gene located on chromosome 5q21 known as adenomatous polyposis coli (APC). Although rare, it is of interest as FAP has provided significant insights into colorectal carcinogenesis, particularly as acquired mutations of APC are common in sporadic colorectal cancers.
The only effective treatment is prophylactic resection of the the large bowel. Surgical options include:
- sub-total colectomy, with regular surveillance of rectal remnant
Although, its most prominent feature is the development of colorectal cancer, several other features are described.