AUTOSOMAL-DOMINANT RETINITIS-PIGMENTOSA WITH APPARENT INCOMPLETE PENETRANCE - A CLINICAL, ELECTROPHYSIOLOGICAL, PSYCHOPHYSICAL, AND MOLECULAR-GENETIC STUDY

Twenty five symptomatic individuals and six asymptomatic obligate gene carriers from four families with autosomal dominant retinitis pigment osa (adRP) showing apparent incomplete penetrance have been studied. S ymptomatic individuals from three families showed early onset of night blindness, non-recordable rod electroretinograms, and marked elevatio n of both rod and cone thresholds in all subjects tested. In the fourt h family, there was more variation in the age of onset of night blindn ess and some symptomatic individuals showed well preserved rod and con e function in some retinal areas. All asymptomatic individuals tested had evidence of mild abnormalities of rod and cone function, indicatin g that these families show marked variation in expressivity rather tha n true non-penetrance of the adRP gene. No mutations of the rhodopsin or RDS genes were found in these families and the precise genetic muta tion(s) remain to be identified.