Clinical significance of extra-colonic manifestations of familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is an inherited autosomal dominant disorder. It is characterized by the development of hundreds to thousands of adenomatous polyps in the colon and rectum, usually beginning at puberty, with a tendency to undergo malignant transformation by the fifth decade [1].Therefore, surveillance and management protocols have always focused primarily on early detection and prophylactic colectomy in affected persons. These measures have substantially reduced the risk of colorectal adenocarcinoma which was once the main cause of mortality, hence changing significantly the natural history of this disease manifestation. However, genotypic aberrations of the fundamental genetic defect that causes the syndrome, a germ-line mutation in the APC gene, may lead to additional phenotypic expressions in which extra-colonic organs develop neoplasms or other changes (Table 1). There is a large diversity in the expression and complexity of these extra-colonic manifestations (EM). Although some appear as clinically non-significant or are only cosmetically disturbing, others are potentially associated with high rates of morbidity and mortality. In contrary to the relatively straightforward management strategy of the colonic manifestation of the syndrome, some EM, like involvement of the upper GI tract and intra-abdominal desmoids, may be difficult to manage. This chapter describes the clinical significance of these anifestations and suggests management and surveillance strategies.