KCNV 2- Associated Retinopathy: Genetics, Electrophysiology, and Clinical Course— KCNV 2 Study Group Report 1

• Published in: American journal of ophthalmology Vol. 225; p. 95
• Main Authors: Georgiou, Michalis, Robson, Anthony G, Fujinami, Kaoru, Leo, Shaun M, Vincent, Ajoy, Nasser, Fadi, Thales Antônio Cabral De Guimarães, Khateb, Samer, Pontikos, Nikolas, Yu Fujinami-Yokokawa, Liu, Xiao, Tsunoda, Kazushige, Hayashi, Takaaki, Vargas, Mauricio E, Thiadens, Alberta AHJ, de Carvalho, Emanuel R, Xuan-Thanh-An, Nguyen, Gavin, Arno, Mahroo, Omar A, Martin-Merida, Maria Inmaculada, Jimenez-Rolando, Belen, Gordo, Gema, Carreño, Ester, Ayuso, Carmen, Dror, Sharon, Kohl, Susanne, Huckfeldt, Rachel M, Wissinger, Bernd, Boon, Camiel JF, Banin, Eyal, Pennesi, Mark E, Khan, Arif O, Webster, Andrew R, Eberhart Zrenner, Héon, Elise, Michaelides, Michel
• Format: Journal Article
• Language: English
• Published: Chicago Elsevier Limited 01.05.2021
• Subjects: Disease; Electrodes; Families & family life; Genetics; Genomes; Hospitals; Neural networks; Patients; Photoreceptors; United Kingdom > UK; United States > US; United Arab Emirates; Germany; Abu Dhabi United Arab Emirates
• ISSN: 0002-9394; 1879-1891
• DOI: 10.1016/j.ajo.2020.11.022

PurposeTo investigate genetics, electrophysiology, and clinical course of KCNV2-associated retinopathy in a cohort of children and adults.Study designThis was a multicenter international clinical cohort study.MethodsReview of clinical notes and molecular genetic testing. Full-field electroretinography (ERG) recordings, incorporating the international standards, were reviewed and quantified and compared with age and recordings from control subjects.ResultsIn total, 230 disease-associated alleles were identified from 117 patients, corresponding to 75 different KCNV2 variants, with 28 being novel. The mean age of onset was 3.9 years old. All patients were symptomatic before 12 years of age (range, 0-11 years). Decreased visual acuity was present in all patients, and 4 other symptoms were common: reduced color vision (78.6%), photophobia (53.5%), nyctalopia (43.6%), and nystagmus (38.6%). After a mean follow-up of 8.4 years, the mean best-corrected visual acuity (BCVA ± SD) decreased from 0.81 ± 0.27 to 0.90 ± 0.31 logarithm of minimal angle of resolution. Full-field ERGs showed pathognomonic waveform features. Quantitative assessment revealed a wide range of ERG amplitudes and peak times, with a mean rate of age-associated reduction indistinguishable from the control group. Mean amplitude reductions for the dark-adapted 0.01 ERG, dark-adapted 10 ERG a-wave, and LA 3.0 30 Hz and LA3 ERG b-waves were 55%, 21%, 48%, and 74%, respectively compared with control values. Peak times showed stability across 6 decades.ConclusionIn KCNV2-associated retinopathy, full-field ERGs are diagnostic and consistent with largely stable peripheral retinal dysfunction. Report 1 highlights the severity of the clinical phenotype and established a large cohort of patients, emphasizing the unmet need for trials of novel therapeutics.