Abstract
Background/Objectives: Biallelic pathogenic variants in the CEP290 gene are typically associated with severe, early-onset inherited retinal dystrophies (IRDs) in both syndromic and non-syndromic forms. This study explores the phenotypic variability of non-syndromic IRDs associated with CEP290 variants, focusing on two siblings with biallelic variants, one of whom exhibits a remarkably mild phenotype, thereby expanding the clinical spectrum. Methods: Whole-exome sequencing (WES) and mRNA analysis were performed to identify and characterize CEP290 variants in the siblings. Comprehensive ophthalmologic evaluations assessed retinal function and disease progression. Results: Two CEP290 variants, a frameshift (c.955del, p.(Ser319LeufsTer16)) and a missense (c.5777G>C, p.(Arg1926Pro)), were identified in trans in both siblings. Despite sharing the same genetic variants, the sister exhibited significantly preserved retinal function, while the brother presented with a more severe, progressive retinal dystrophy. Conclusions: This study broadens the phenotypic spectrum of non-syndromic CEP290-related IRDs, demonstrating variability in disease severity ranging from mild to severe. These findings highlight the importance of personalized monitoring and tailored management strategies based on individual clinical presentations of CEP290-related IRDs.