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Ajoy Vincent, Elise Heon; The range of retinal phenotypes in CNGB3 related disease. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2764. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To describe in detail the phenotypic and genotypic characteristics of CNGB3-related disease in a molecularly confirmed cohort.
A retrospective review of twelve cases (Age Range: 2 – 36 years; Mean: 12.16 years; Median 7 years) with two pathogenic mutations in CNGB3 was performed. Details of clinical history, best corrected visual acuity (BCVA) measurements, refraction, retinal evaluation and full-field electroretinography were obtained from all cases. Spectral domain optical coherence tomography (SD-OCT) images were reviewed from 11 cases. Contrast sensitivity and color vision testing results were included when available.
Photophobia was reported in all cases; nine (75%) had history of nystagmus. BCVA ranged between 20/60 – 20/400 in eleven cases; the youngest child (2 years) fixed and followed light. Six cases had hyperopia or hyperopic astigmatism, and four cases had mixed astigmatism. Color vision tests (HRR and/or D15) showed wide variability, and ranged between being normal to demonstrating severe trichanomalous defects. Dull foveal reflex was noted in nine cases (75%), and macular atrophy was seen in one case. Scotopic electroretinogram (ERG) responses were normal in 11 cases; one case had borderline scotopic ERG amplitudes. The photopic ERG responses were non-detectable or markedly attenuated in 9 cases; three other cases had detectable photopic ERGs. The SD-OCT raster scans showed disruption in the photo-receptor outer segments (OS), ellipsoid zone and inner segments (IS) within the foveal region in seven cases. Presence of inner retinal layers at the fovea consistent with foveal hypoplasia was noted in 6 cases; two cases demonstrated an optical gap involving the OS in the central sub-foveal zone. The frame-shifting variant c.1148delC (p.Thr383fsx13) was the commonest mutation identified (16/24 alleles), and was found in homozygous state in five cases. All cases that harbored the c.1148delC variant in homozygous state had non-detectable photopic ERG responses.
Achromatopsia, the commonest CNGB3 phenotype, was observed in ten cases; oligocone trichromacy and maculopathy phenotypes were found in one case each. Progressive color vision loss was noted in one case. Foveal hypoplasia, a developmental anomaly was observed in 50% of cases in this series.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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