Diagnostic value of fundus examination in familial adenomatous polyposis.

BACKGROUND Multiple, bilateral lesions of congenital hypertrophy of the retinal pigment epithelium (CHRPE) have been described in patients suffering from familial adenomatous polyposis (FAP) since 1980. This study aimed to determine a reliable diagnostic criterion, based on the size and number of retinal CHRPE lesions, allowing the screening of patient carriers of the gene responsible for FAP. METHODS 32 control subjects and 144 patients belonging to 85 FAP families were studied, divided into 124 carriers of the genetic alteration and 20 non-carriers. RESULTS In carriers of the deleted gene, multiple, bilateral retinal lesions were consistently observed. Lesion situation, size, shape, and degree of pigmentation were variable however. A positive criterion for FAP was defined as the presence of at least four lesions whatever their size, or at least two lesions one of which is large. This criterion showed a high sensitivity (0.68) and a maximal specificity (1). Within each family, the retinal phenotypic expression was homogeneous. CHRPE lesions were observed in two thirds of the FAP families and absent from the remaining third. CONCLUSION By using this new positive diagnostic criterion, fundus examination allows early detection of those children carrying the gene responsible for FAP in families positive at ocular examination.