Hereditary renal-retinal dysplasia.

Juvenile nephronophthisis and medullary cystic diseases are inherited kidney disorders leading to end stage uremia. As these diseases appear to be identical, they were grouped together in nephronophthisis-cystic renal medulla complex. Among its extrarenal manifestations, tapeto-retinal degeneration is the most frequent allied condition. This specific association of the renal and retinal conditions, suggesting a genetic background, is called hereditary renal-retinal dysplasia and is transmitted as an autosomal recessive trait. There are some variations in the type of the retinal degeneration in renal-retinal dysplasia and similar basic genetic mechanisms may results in Leber's congenital amaurosis, or retinitis pigmentosa, central retinal degeneration or stationary congenital night blindness. Pleiotropism seems to be responsible for the spectrum of these anomalies. Occasional expression in the heterozygous state by urinary concentrating disabilities or electroretinographic impairments were documented. The nature and pathogenesis of renal-retinal dysplasia remain a debated issue, but some evidence supports the possibility of an inborn error of metabolism causing the basic defects.