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

This research describes a case of a baby diagnosed with Bardet-Biedl Syndrome (BBS) before birth. BBS is a rare inherited condition that affects multiple parts of the body, including the eyes, kidneys, hands and feet, brain development, and reproductive organs. During a routine pregnancy ultrasound at 17 weeks, doctors noticed the baby had enlarged kidneys. They then performed genetic testing and found that the baby had inherited two different genetic changes (mutations) in the BBS7 gene - one small change and one larger deletion of genetic material. What makes this case special is that the baby also had an extra piece of ear tissue (accessory auricle), which hasn't been commonly reported in BBS before. The researchers found that large deletions of genetic material (called copy number variants) may be more important in causing BBS than previously thought. This finding could help doctors better diagnose BBS, especially during pregnancy when genetic testing is performed. This research expands our understanding of what BBS can look like and how it's caused genetically. For families affected by BBS, this information could lead to better genetic counseling and earlier, more accurate diagnosis during pregnancy. However, this study focuses on diagnosis rather than new treatments.

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.