To describe young monozygotic twin sisters with fundus albipunctatus(a type of autosomal recessive stationary night blindness caused by mutationsof the 11-cis retinol dehydrogenase gene [RDH5]) associated with cone dystrophy, previously reported in elderlymen.
Ophthalmologic examinations were performed, and the RDH5 gene was analyzed by direct genomic sequencing.
Twin 23-year-old sisters with high myopic refractive errors of approximately−13 diopters were diagnosed as having fundus albipunctatus. Their photopicelectroretinographic responses were markedly reduced, and cone dystrophy wasdiagnosed. One twin had macular degeneration with reduced best-corrected visualacuity, while the other twin had normal maculae with good visual acuity. Acompound heterozygous mutation, Val132Met and Arg280His, in the RDH5 gene was found in both sisters.
Cone dystrophy can be present in patients with fundus albipunctatus,not only elderly men but also young women. The clinical severity differedbetween monozygotic twins with fundus albipunctatus and cone dystrophy.
The patient's sex is not critical for the presence of cone dystrophyin patients with fundus albipunctatus. The discordant findings in the twinsindicate that factors other than genetics influenced the phenotype.