Gastrointestinal Polyposis: Syndromes and Genetic Mechanisms.

Adenomas and hamartomas, two genetically transmitted histologic types of gastrointestinal polyposis, are associated in syndromes with extragastrointestinal manifestations. Adenomas that predispose to adenocarcinoma are basic to familial polyposis coli, the Gardner syndrome and the Turcot syndrome. Gastrointestinal polyps and extragastrointestinal lesions serve as a warning, providing time for diagnosis and treatment of adenomas to prevent their malignant transformation in patients and their relatives. Hamartomas with no malignancy potential, but having a tendency toward bleeding and bowel obstruction, are associated with the Peutz-Jeghers syndrome, juvenile polyposis, multiple hamartoma syndrome, basal-cell nevus syndrome and the Cronkhite-Canada syndrome. Most of these lesions and syndromes follow the inheritance pattern of a single autosomal dominant gene.