Familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is a rare disorder associated with less than 1% of colorectal carcinomas (CRCs). Since FAP is a potentially preventable cause of CRC clinicians should have an adequate knowledge of it to identify the disease and to manage the patient and family. FAP is an autosomal dominant inherited disorder characterised by the development of more than a hundred adenomatous polyps in the colon and rectum which can undergo malignant change. Children of an affected individual are at 50% risk of inheriting the predisposing gene. After the identification of an index patient, genetic testing in combination with the detection of extra-colonic manifestations allows more accurate identification of family members likely to have the faulty gene, enabling the targetting of screening and preventive surgery only to those at risk. FAP also provides insights into the development, progression and prevention of sporadic CRC.