A Rare Case of Bardet-Biedl Syndrome Caused by a Heterozygous Point Variant in BBS7 and a CNV Involved BBS7

Bardet-Biedl syndrome (BBS) is a rare autosomal recessive disorder classified as a multisystem nonmotile ciliopathy, primarily characterized by retinal cone-rod dystrophy, central obesity, postaxial polydactyly, cognitive impairment, kidney disease, and abnormalities of hypogonadism and genitourinary.

A fetus presenting with enlarged kidneys and enhanced echogenicity was identified during a prenatal screening at 17 weeks of gestation. Genetic analysis of the fetus was performed using chromosomal microarray analysis (CMA) and clinical exome sequencing (CES). The prenatal assessment yielded notable results in the fetus, with CMA and CES analysis detecting a compound heterozygous variant in the BBS7 gene and a substantial deletion in the chromosomal region 4q26q27. Subsequent autopsy findings corroborate the presence of postaxial polydactyly, bilateral renal enlargement, and an accessory auricle in the fetus.

Our study expands the range of phenotypes associated with BBS to include bilateral accessory auricle, as well as broadens the spectrum of variants linked to BBS. Our findings support the significant contribution of copy number variants to BBS, offering clinicians valuable insights for diagnosing the condition, particularly in prenatal settings.