Congenital hypertrophy of the retinal pigment epithelium.

The flat, circumscribed, and hyperpigmented lesion of the retinal pigment epithelium (RPE) without clinically apparent involvement of the overlying retina, designated as congenital hypertrophy, was found to be associated with corresponding scotomas in the visual field. The depth of the scotoma increased with the age of the patient. These lesions did not grow. They could be readily differentiated from other pigmented fundus lesions on the basis of their typical clinical appearance. Histopathology revealed a single layer of hypertrophied cells, containing numerous large pigment granules, and degeneration of photoreceptor cells overlying the area of abnormal RPE. The clinical as well as the histologic findings suggested that the retinal abnormality overlying the hypertrophied RPE was due to secondary degeneration rather than primary maldevelopment of photoreceptor cells.