Grouped congenital hypertrophy of the retinal pigment epithelium follows developmental patterns of pigmentary mosaicism.

Abstract

To determine whether sectorial-oriented grouped pigmentations of the retina follow developmental patterns of pigmentary mosaicism. Systematic literature review. Fundus images from patients with grouped congenital hypertrophy of the retinal pigment epithelium (CHRPE). An extensive Internet and library search was performed to obtain articles dealing with grouped CHRPE. Each article was carefully screened for fundus images and inclusion criteria. Fundus images of sufficient quality were scanned, digitized, and matched in size using Adobe Photo Shop to compare the pattern location and extension of the pigmented lesion. These obtained patterns of grouped CHRPE were than mapped and superimposed. Forty-five images were retrieved from 32 articles with grouped CHRPE. The lesions extended from the margin of the optic disc and radiated in sectors to the fundus periphery. The stream of growth did not follow the pattern of the retinal nerve fiber layer, because the clusters of pigmented cells crossed the midline raphe not sparing the macular area. Smaller lesion clusters were mainly located near the optic disc, whereas larger lesions were found in the periphery. The growth pattern of grouped CHRPE is similar to cutaneous sectorial pigmentations. We speculate that pigmentary mosaicisms may be a modified wild-type allele in a somatic cell clone during early embryogenesis following developmental lines analogous to the cutaneous lines of Blaschko. The sectorial pigmentations on the ocular fundus may reflect the stream, outgrowth, and migration of retinal pigment epithelium cells during embryogenesis.