Gastroenterology · UKMLA & AKT
Familial adenomatous polyposis (FAP)
A free high-yield preview for the UKMLA Applied Knowledge Test, covering how to recognise this condition. The full SA Note notes add investigations, management and complications, with practice questions on this topic.
Key high-yield points
- Autosomal dominant - germline mutation in APC gene (chromosome 5q21)
- NOT the most common inherited colorectal cancer - that is Lynch syndrome (HNPCC) (~3-5%); FAP accounts for <1%
- Near-100% lifetime risk of colorectal cancer if untreated; mean age of cancer ~35-40 years
- Hundreds to thousands of adenomatous polyps developing from teens onward
FAP vs Lynch syndrome: Lynch syndrome is the most common inherited colorectal cancer. FAP is more dramatic (100% penetrance, thousands of polyps) but far less common.
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