Comprehensive clinical and genetic characterization of Bardet-Biedl Syndrome: insights from the largest Turkish cohort.

Bardet-Biedl Syndrome (BBS) is a rare, pleiotropic ciliopathy involving retinal dystrophy, polydactyly, obesity, and renal abnormalities. Despite growing knowledge of its genetic basis, data from populations with high rates of consanguinity remain limited. This study presents the largest genetically confirmed BBS cohort reported from Türkiye, consisting of 25 individuals who underwent clinical exome-based multigene panel testing. Biallelic pathogenic variants were identified in all patients, including three novel variants in the ARL6/BBS3, BBS9, and BBS10 genes, observed in four patients, including two siblings. Retinal dystrophy was the most common feature (94.1%), followed by polydactyly (88.0%), obesity (68.0%), and renal anomalies (52.0%). Genotype-phenotype comparisons highlighted notable variability, particularly among individuals with BBS1 and BBS10 pathogenic variants, consistent with prior international cohorts. This cohort underscores the clinical heterogeneity of BBS and reveals potential population-specific patterns shaped by consanguinity and genetic background. Our findings support the utility of multigene panels in clinical diagnosis and provide a basis for national registries and targeted care strategies for rare inherited diseases in underrepresented populations.