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T. Gekka, T. Hayashi, T. Takeuchi, Y. Ueoka, K. Kitahara; A Novel Frameshift RS1 Mutation (E62DfsX22) in a Japanese Patient With X-Linked Retinoschisis. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1668. doi: https://doi.org/.
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X-linked retinoschisis (XLRS) is a hereditary retinal disorder with macular degeneration. Affected males have characteristic foveal schisis and reduced b-wave amplitudes in standard combined full-field electroretinograms (ERGs). More than 150 RS1 mutations have been previously reported since the initial RS1-mutation report in 1997. Genotype-phenotype comparisons have revealed that no significant correlations between mutation type and disease severity. In fact, genetic testing is used to diagnose XLRS patients including ambiguous patients, and to provide genetic counseling. To report a novel mutation in the RS1 gene and clinical features in a Japanese XLRS patient.
In a 17-year-old male proband, best-corrected visual acuity (BCVA), funduscopy, fluorescein angiography (FA), optical coherence tomography (OCT) and full-field ERG were performed. Blood samples were obtained from the proband and his mother. The RS1 gene analysis for mutation was performed using polymerase chain reaction (PCR). The PCR products were purified and directly sequenced.
BCVA was 0.4 in both eyes. The proband had foveal schisis without fluorescein leakage. Peripheral retinoschisis was not observed. The OCT images revealed foveal schisis with parafoveal lamellar schisis. The full-field ERGs showed normal rod, cone, 30-Hz flicker responses and reduced standard combined b-wave responses, but not typical negative type. In the proband, we identified a 1-bp (T) insertion mutation (c.185_186insT) in exon 4, which causes frameshift and results in a truncated protein (p.E62DfsX22). His unaffected mother, who was a heterozygote for the mutation, had no abnormalities in funduscopy and OCT.
The RS1 mutation that has been unreported is responsible for the XLRS patient in whom the characteristic OCT and ERG findings were found. Identification of the RS1 mutation is helpful for accurate diagnosis of XLRS and genetic counseling for family members.
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