Congenital hypertrophy of the pigment epithelium: light microscopic and ultrastructural findings in young children.

Two cases of autoptically observed congenital hypertrophy of the retinal pigment epithelium (CHRPE) in a newborn and in an infant, one with electron photomicrographs, are presented. In contrast to the adjacent RPE cells, the apical cellular surface of CHRPE cells shows only rare small microvilli, mostly at the cell border. The prominent findings are large pigment granules from 3.5 to 8 microns protruding towards the apical cellular surface. These macromelanosomes do not exhibit coalescence as noted by others, but show a concentric lamellar structure that may be the result of a disturbed development sequence in melanin granule formation. The authors' observation of CHRPE in a newborn and in an infant suggests that the term congenital HRPE is appropriate. The presence of these changes at this early age is consistent with the condition being a primary failure of differentiation. Finally, the authors present evidence of a disturbed melanogenesis in CHRPE cells resulting in macromelanosomes formation.