Purpose: The aim of this study is to characterize the clinical features of four unrelated Chinese patients with retinal dehydrogenase 5 (RDH5) retinopathy (fundus albipunctatus) and to identify the genetic defects underlying this disorder.
Methods: Complete ophthalmic examinations, including slit-lamp biomicroscopy, dilated indirect ophthalmoscopy, spectral domain optical coherence tomography, and full-field electroretinography were performed. Genomic DNA was prepared from peripheral venous leukocytes. Polymerase chain reaction and direct sequencing were used to screen the coding exons and exon/intron boundaries of the RDH5 gene (11-cis-retinol dehydrogenase).
Results: Four patients with RDH5 retinopathy, including two 6-year-old boys, from 4 unrelated Chinese families were recruited in this study. A novel c.832C>T (p.Arg278Ter) nonsense mutation of the RDH5 gene was identified in one 6-year-old boy, who has a compound heterozygous mutation with c.928delC/InsGAAG (p.Leu310GluVal). Homozygous Leu310GluVal mutations were identified in 2 male patients including the other 6-year-old boy. The other patient was a 29-year-old woman in whom compound heterozygous changes c.500G>A (p.Arg167His) and Leu310GluVal in RDH5 were identified. All patients manifested the fundus phenotype of fundus albipunctatus. Electroretinograms recorded in 1 boy (Case 3) showed scotopic waveforms within normal range under standard conditions and no change after prolonged dark adaptation. Scotopic waveforms were within the normal range for Case 4 while higher amplitudes (30% increase) were recorded after prolonged dark adaptation. The two adult patients had depressed scotopic electroretinogram responses under standard conditions. Optical coherence tomography showed discrete highly reflective lesions extending from the retinal pigment epithelium to the level of the external limiting membrane.
Conclusion: A novel c.832C>T (p.Arg278Ter) nonsense mutation in RDH5 was identified. A specific mutation, Leu310GluVal, was seen in the homozygous state in one adult male and one boy and in the heterozygous state in one female adult and one boy with RDH5 retinopathy, suggesting a common mutation. Preserved rod function was observed in one young subject in this study.