[Diffuse familial polyposis].
Familial gastrointestinal polyposis constitutes a multiplication of the principle varieties of common polyps, not only in the colon but also in other parts of the gastrointestinal tract. These are hereditary and familial diseases with autosomal dominant transmission. The genetic defect can also be responsible for associated extra-gastrointestinal lesions. The classification of these familial polyposes is based on the histological features of the polyps. The adenomatous polyposes consist of familial recto-colonic polyposis (FRCP), which is the most frequent form, and Gardner's syndrome. This variety of polyposis selectively involves the recto-colon, but also presents gastric and duodenal lesions. The defining feature of Gardner's syndrome is the extra-gastrointestinal mesenchymal lesions, osteomas, skin tumours and, most importantly, mesenteric fibromatosis which may complicate abdominal operations. The prognosis of FRCP and Gardner's syndrome is determined by the almost obligatory and often multicentric malignant degeneration of the polyps, which justifies routine total proctocolectomy. Peutz-Jeghers' syndrome is syndrome is characterised by hamartomatous polyposis selectively involving the upper part of the small intestine. It generally has a benign course. Similarly, juvenile polyposis consists of benign inflammatory polyps and is accompanied by congenital anomalies in one third of cases. The diagnosis of familial polyposis should be proposed whenever polyps are detected, which appear to be unusual in terms of their number or their distribution. A family survey should be performed in such cases.