Non-syndromic adult-onset rod-cone dystrophy

PURPOSE: The purpose of this study is to characterize phenotypes and genotypes of non-syndromic adult-onset rod-cone dystrophy (RCD) in the United Arab Emirates (UAE). METHODS: Retrospective series of consecutive Emirati patients referred to the Ocular Genetics Service of Cleveland Clinic Abu Dhabi (2016-2023, inclusive) who were diagnosed with non-syndromic RCD after childhood (symptomatic at or after 16 years old) and for whom a molecular diagnosis was made after diagnostic genetic testing guided by clinical phenotype (single gene, next-generation panel, or exome sequencing). RESULTS: Twenty-four cases (15 male; 19 families) were identified. Autosomal recessive typical RCD was most common (17/19 families, 89%), related to homozygous variants in PCARE (8), EYS (3), AGBL5 (3), and CYP4V2 (1). Atypical early macular involvement was noted in seven unrelated cases; identified genes were CDHR1 (5) and CERKL (2). Autosomal dominant RCD was noted in two cases, related to TOPORS and PRPF31. Regarding PCARE-related disease, 7/8 cases (3/4 families) harbored the same homozygous pathogenic variant (c.2967del; p.Val990Trpfs*45). There were no other recurrent variants among families. CONCLUSION: PCARE: c.2967del; p.Val990Trpfs*45 likely represents founder effect. Atypical early macular involvement suggests variants in CDHR1 or, less commonly, CERKL. While autosomal recessive cause predominates, autosomal dominant cause can occur.