Bardet-Biedl Syndrome in Four Siblings: Clinical and Genetic Insights From a Rare Familial Cluster

Bardet-Biedl syndrome (BBS) is a rare autosomal recessive ciliopathy with multisystem involvement, including retinal dystrophy, obesity, polydactyly, renal anomalies, hypogonadism, and cognitive impairment. Early diagnosis is often delayed due to gradual symptom onset. The revised diagnostic criteria for BBS, considering molecular diagnosis, ensures diagnostic certainty.

We report a case of a 15-year-old girl born out of a nonconsanguineous marriage with delayed puberty, progressive vision loss, and obesity. Family history revealed similar symptoms in her 3 younger siblings. All four fulfilled diagnostic criteria for BBS. Whole exome sequencing in the index case and Sanger sequencing in the other 3 siblings identified a pathogenic homozygous 1 base pair deletion in exon 3 of the MKKS gene (p.Ser236Ter), confirming BBS type 6.

BBS is a clinically and genetically heterogeneous disorder. Genetic confirmation aids early diagnosis, enabling timely intervention and multidisciplinary management to alleviate the burdensome complications.

This case highlights the importance of early recognition and genetic confirmation in BBS, even in the background of nonconsanguinity. Early diagnosis can improve quality of life and long-term outcomes.