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Rola Ba-Abbad, Gavin Arno, Omar Abdul Rahman Mahroo, Michel Michaelides, Andrew Webster, Anthony G Robson; Clinical and molecular characterization of autosomal recessive and X-linked incomplete congenital stationary night blindness. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5950.
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© ARVO (1962-2015); The Authors (2016-present)
To describe the clinical and electrophysiological features of incomplete congenital stationary night blindness (iCSNB) due to disease-causing variants in CACNA1F and CABP4.
Retrospective study assessing the clinical, molecular, and electrophysiological characteristics of retinopathy in patients with iCSNB, reviewed at Moorfields Eye Hospital. International-standard electroretinography (ERG) was performed under dark-adapted (DA) and light-adapted (LA) conditions, in patients with clinical signs and symptoms of retinal dysfunction. Patients with clinical diagnosis of iCSNB underwent molecular testing using next generation sequencing, whole exome, or whole genome sequencing.
Thirty-seven patients were identified. Thirty-two patients (5–72 years) were hemizygous for variants in CACNA1F (23 nonsense or frameshift, 5 missense). Five patients (5-47 years) had bi-allelic variants in CABP4 (4 nonsense or frameshift, 1 deletion < 1 kb abolishing exon 6). Pediatric ERG protocols were used for 10 patients with CACNA1F retinopathy and one patient with CABP4 retinopathy, and were excluded from quantitative ERG analysis. Patients harboring CACNA1F variants had variable visual acuity (20/15-20/200), nystagmus (38%), myopia (53%) or hypermetropia (19%), nyctalopia (15%), and photoaversion (6%). All patients with CABP4 variants had severely reduced vision (20/200-20/500), nystagmus (80%), photoaversion (60%), and dyschromatopsia (60%). Retinal examination was unremarkable in either disorder. The DA 10 ERG a- and b-wave amplitudes overlapped between the CACNA1F and CABP4 groups; all had electronegative waveforms, but the range of b:a ratios in the CACNA1F cases (range 0.36 –1.01) extended to higher values than those for CABP4 (range: 0.4–0.58). The LA 3.0, single flash cone ERGs were smaller in the CABP4 group: a-wave, range 0–20 µV; b-wave range 0–30 µV, than some of the cases with CACNA1F-retinopathy: a-wave, range 10–60 µV; b-wave, range 15–65 µV.
The visual symptoms and retinal dysfunction in CABP4 retinopathy are more severe than in CACNA1F retinopathy, suggesting different roles of the two proteins in rod and cone systems.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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