Purpose:
To describe the early clinical and electrophysiological features of cone-rod dystrophy due to a mutation of cadherin-related family member 1 (CDHR1).
Methods:
Three affected siblings from a consanguineous family were ascertained. The clinical data included retinal examination, Goldmann visual fields, fundus autofluorescence imaging, optical coherence tomography (OCT), and pattern and full-field electroretinograms. Exome sequencing was performed in two siblings.
Results:
The three siblings presented at age 24, 18, and 16 years, respectively. Their main symptoms were blurred central vision, dyschromatopsia, and photoaversion. All were myopic with best-corrected visual acuities of 20/60, 20/60, and 20/40, respectively. Fundoscopy revealed a range of macular appearances from mild retinal pigment epithelial changes to symmetric, subfoveal pigmented lesions. Fundus autofluorescence imaging and OCT revealed evidence of mild structural abnormalities in the two older siblings. Electroretinography findings in all three patients indicated severe generalized cone-rod dysfunction. Mutational screening in the three siblings showed them to be homozygous for a previously reported frame-shifting mutation in exon 13 of CDHR1, c.1463delG, p.G488fs.
Conclusions:
The initial clinical signs in this specific retinopathy may be relatively subtle despite a significant functional deficit, with unusual, bilateral, subfoveal pigmented lesions in one 16-year-old patient. Lack of CDHR1 in the human retina causes symptoms related to cone photoreceptor dysfunction in the first instance. A near-normal retinal structure, at least in the first two decades, suggests that CDHR1-related retinopathy may be a good candidate for gene replacement or other novel stabilizing treatments.