Value of congenital hypertrophy of the retinal pigment epithelium as diagnostic marker in familial adenomatous polyposis.

Abstract

Familial Adenomatous Polyposis (FAP) is a dominant autosomic disease characterized by the development of hundreds to thousands of colonic adenomatous polyps. Affected patients have a 100% risk of colon cancer development if they are not submitted to a prophylactic colectomy. Identification of carriers depends on the detection of colonic polyps, and endoscopic surveillance must be offered to all descendents, including healthy individuals. Congenital hypertrophy of the retinal pigment epithelium (CHRPE) has been suggested to have a correlation with FAP trait, even before colonic polyp development. The objective of this study is to evaluate CHRPE as a diagnostic marker in FAP patients and descendents. CHRPE was studied in 26 members of 7 FAP families, using direct and indirect ophthalmoscopy, biomicroscopy and retinography. It was found in 62.5% of patients and in 10% of the descendents at risk. Two families did not show signs of CHRPE. Affected members in the remaining families, had positive examinations in 83.3% (two affected members were negative). These results suggest that CHRPE is an important diagnostic tool to identify FAP patients in those families which express the marker. To those descendents who have negative examinations, whether they belong to positive or negative CHRPE families, identification of FAP trait depends on endoscopic surveillance in order to detect colonic polyps.