Familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is a paediatric blind spot. Most paediatricians consider it a disorder that falls under the remit of geneticists, surgeons, or gastroenterologists but all should be aware of the condition. FAP is characterised by the development of adenomatous polyps in the colorectum, in some cases numbering in excess of a thousand. In a known family, even a single polyp is virtually diagnostic, though such a polyp must be histologically distinguished from a juvenile polyp. The birth prevalence of FAP is about one in 80001 and over half develop polyps under the age of 16. Screening usually starts around puberty, although rarely malignancy can develop as young as 5 or 6 years.24 Extra colonic tumour both benign and malignant can also occur that is, hepatoblastoma, intracranial tumours, benign cystic osteomas of the jaw,5 desmoid tumours, and multiple sebaceous cysts. The presence of these features in the past attracted the diagnostic label of Gardner's syndrome. Recent molecular genetic studies, however, have confirmed the clinical suspicion that Gardner's syndrome and FAP are the same condition. Congenital hypertrophy of the retinal pigment epithelium (CHRPE) was first described in individuals with Gardner's syndrome.6 Subsequent analysis showed that the majority of gene carriers could be distinguished from the normal population by the presence of these benign retinal pigment defects.7 The presence of five or more such lesions on indirect fundoscopy may be regarded as diagnostic particularly if they include large lesions.8