Familial Adenomatous Polyposis (FAP)

What is FAP?

FAP—an autosomal dominant condition caused by mutation in the APC tumour suppressor gene on chromosome 5—is characterized by the development during the second decade of life of hundreds of adenomas in the colon and rectum. These eventually cause rectal bleeding or anaemia, or develop into cancer.

A less aggressive variant—termed attenuated FAP, is characterized by fewer colorectal adenomatous polyps (usually 10–100), a later age of denoma appearance and a lower cancer risk.

What are the Symptoms of FAP?

FAP is initially symptomless but later gastrointestinal features appear. Extraintestinal manifestations may include osteomas, dental anomalies (unerupted teeth, agenesis of one or more teeth, supernumerary teeth, dentigerous cysts and odontomas), congenital hypertrophy of retinal pigment epithelium, desmoid tumours and extracolonic cancers (thyroid, liver, bile ducts and central nervous system).

Where there are skull and mandible osteomas, dental abnormalities and fibromas on scalp, shoulders, arms and back, the term Gardner syndrome is employed.

How is FAP Diagnosed?

Clinical plus imaging and colonic polyp biopsy.

How is FAP Treated?

The intestinal polyps have a 100% risk of undergoing malignant transformation: therefore, the early identification of disease and colectomy is critical.


Reference: Scully C. 2010. Oral and Maxillofacial Disease. Vol. 4th Ed. Informa Healthcare. UK.