# Gene Duplication in a Patient With Usher Syndrome Type 2C: A Case Report

## TL;DR

A 34-year-old man with Usher syndrome type 2C was found to have a gene duplication in ADGRV1, highlighting how genetic variants affect disease severity.

## Contribution

This case report identifies a novel homozygous gene duplication in ADGRV1 associated with Usher syndrome type 2C.

## Key findings

- The patient exhibited classic symptoms of Usher syndrome type 2C, including hearing loss and retinitis pigmentosa.
- Genetic testing revealed a homozygous pathogenic copy number variation in exons 79-84 of the ADGRV1 gene.
- The case emphasizes the importance of variant-specific diagnosis in hereditary diseases like Usher syndrome.

## Abstract

Variants of the ADGRV1 gene cause Usher syndrome type 2C (USH2C). There are three types of Usher syndrome, all inherited in an autosomal recessive pattern. USH2C classically causes sensorineural hearing loss and progressive retinitis pigmentosa (RP) occurring in adolescence or adulthood. In this study, we report the case of a 34-year-old male with congenital sensorineural and progressive hearing loss and peripheral vision loss with a fundus examination of pale optic nerve with a cup-to-disk ratio of 0.40, arteriolar attenuation, arteriovenous ratio 2/5 with choroid-retinal degeneration, peripheral bony spicules, and fundus tessellation. Visual field test (30-2 Carl Zeiss Meditec, Inc.) showed that the patient had a mean deviation of -21.22 dB (p < 0.5) and 7.51 dB (p < 0.5) in the right and left eye, respectively. Upon full-field electroretinogram (ERG), the patient had non-recordable photopic and scotopic ERG responses bilaterally. The patient’s macular optical coherence tomography showed an average thickness of 221 µm and a total macular volume of 8 mm3 in the right eye, and an average thickness of 215 µm and a total macular volume of 7.8 mm3 in the left eye. Based on these ocular findings, the patient was clinically diagnosed with RP. Genetic testing with exome sequencing showed a homozygous pathogenic copy number variation (4) at exons 79-84 of the ADGRV1 gene. Our case highlights the importance of recognizing the specific type of variant affecting a gene in hereditary diseases such as RP, as disease severity may be influenced by the nature of the variant.