# CDHR1-Associated Retinal Dystrophies: Expanding the Clinical and Genetic Spectrum with a Hungarian Cohort

## TL;DR

This study expands the understanding of CDHR1-related retinal diseases by analyzing a Hungarian patient group, revealing varied symptoms and genetic changes.

## Contribution

The study reports new CDHR1 variants and expands the clinical spectrum of CDHR1-associated retinopathy in a Hungarian cohort.

## Key findings

- Four CDHR1 variants were identified, including a novel splice acceptor site and intronic variant.
- Five distinct retinal dystrophy phenotypes were observed in the cohort.
- Rod-cone dystrophy was the most common phenotype, observed in 55.6% of cases.

## Abstract

Aim: To report on the clinical and genetic spectrum of retinopathy associated with CDHR1 variants in a Hungarian cohort. Methods: A retrospective cohort study was conducted at a single tertiary care referral center. The study enrolled nine patients harboring biallelic variants in the CDHR1 gene. Detailed clinical history, multimodal imaging, electroretinography, and molecular genetics are presented. Results: We identified four CDHR1 variants predicted to cause loss-of-function and five phenotypes (cone dystrophy, central areolar choroidal dystrophy, cone-rod dystrophy, rod-cone dystrophy, and late-onset macular dystrophy). The most frequent variant was the synonymous CDHR1 c.783G>A (p.Pro261=) variant (10/18 alleles, 55.6%). A novel splice acceptor site variant, CDHR1 c.349-1G>A, and a novel intronic variant, CDHR1 c.1168-10A>G, were also detected. Fundus examination revealed macular atrophy with or without peripheral retinal changes. Full-field electroretinography, available in seven patients, demonstrated decreased light-adapted and extinguished dark-adapted responses in both the rod-cone dystrophy group and patients with macular involvement. OCT imaging indicated ellipsoid zone disruption with foveal sparing in two out of nine patients and severe retinal damage in rod-cone dystrophy cases. Conclusions: The predominant clinical manifestations of cone dystrophy, cone-rod dystrophy, and macular dystrophy in the Hungarian patient cohort showed heterogeneity, with a rod-cone dystrophy phenotype observed in five of nine cases (55.6%). The natural history of CDHR1-associated retinopathy typically follows a slow progression, providing a therapeutic window, which makes the disease a candidate for gene therapy.