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Updated: Jun 10, 2026
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Published on: November 17, 2009
Structural and functional characterization of an individual with the M285R KCNV2 hypomorphic allele
Thales A C de Guimaraes1,2, Francesco Lai3, Raffaella Colombatti4
1UCL Institute of Ophthalmology, University College London, London, UK.
Background:
Disease-causing variants in the KCNV2 gene are associated with "cone dystrophy with supernormal rod responses," a rare autosomal recessive retinal dystrophy. There is no previous report of hypomorphic variants in the disease.
Material And Methods:
Medical history, genetic testing, ocular examination, high-resolution retinal imaging including adaptive optics scanning light ophthalmoscopy (AOSLO), and functional assessments.
Results:
A 16-year-old male with mild cone-rod dystrophy presented with reduced central vision and photophobia. Genetic testing showed two variants in KCNV2, c.614_617dupAGCG (p.207AlafsTer166) and c.854T>G (p.Met285Arg), the latter which was previously considered benign. Electrophysiological assessment revealed the pathognomic electroretinogram waveforms associated with KCNV2-retinopathy. Optical coherence tomography showed discrete focal ellipsoid zone disruption, while fundus autofluorescence was normal. Non-waveguiding cones corresponding to areas of loss of photoreceptor integrity were visible on adaptive optics scanning light ophthalmoscopy. Retinal sensitivity and fixation were relatively preserved, with a demonstrable deterioration after 14 months of follow-up.
Conclusions:
We provide functional and structural evidence that the variant M285R is disease-causing if associated with a loss-of-function variant. To the best of our knowledge, this is the first hypomorphic allele reported in KCNV2.
