What is Bardet-Biedl Syndrome

TL;DR: Bardet-Biedl Syndrome (BBS) is a rare, multisystem genetic disorder characterized by a wide range of clinical features, including vision loss, obesity, kidney abnormalities, and polydactyly (extra fingers or toes). It is caused by dysfunction in primary cilia—tiny, hair-like structures on cells—which disrupts how various organs communicate and develop throughout the body.

What is Bardet-Biedl Syndrome?

Bardet-Biedl Syndrome is a complex ciliopathy, meaning it is a disease caused by impaired function of the cilia, which are found in nearly every cell of the human body. Because cilia are essential for sensory perception and cellular signaling, Bardet-Biedl Syndrome affects multiple organ systems simultaneously. While the severity and combination of symptoms vary greatly even within families, the condition is typically characterized by a constellation of primary features that emerge during childhood.

Which body systems are affected by Bardet-Biedl Syndrome?

The multisystem nature of Bardet-Biedl Syndrome means that clinical manifestations are diverse. Patients often experience progressive retinal degeneration, which typically leads to significant vision impairment or blindness. Other common features associated with Bardet-Biedl Syndrome include:

• Vision: Rod-cone dystrophy leading to night blindness and tunnel vision.


• Weight: Early-onset obesity, often starting in childhood.


• Digits: Polydactyly (extra fingers or toes) or syndactyly (fused digits) present at birth.


• Kidneys: Structural abnormalities such as cysts or malformed kidneys, which are a major focus of clinical monitoring.


• Endocrine/Reproductive: Hypogonadism or delayed puberty.


• Cognitive: Learning disabilities or developmental delays, though these range from mild to severe.

How common is Bardet-Biedl Syndrome?

Bardet-Biedl Syndrome is considered a rare disorder with an estimated prevalence ranging from 1 in 100,000 to 1 in 160,000 individuals in North America and Europe. However, these numbers can be higher in specific populations, such as in Newfoundland, Canada, or among certain Bedouin communities, where the founder effect has led to increased frequency. Currently, 121 people with Bardet-Biedl Syndrome have joined the DiseaseMaps.org community to share their experiences and support one another.

Is Bardet-Biedl Syndrome hereditary?

Yes, Bardet-Biedl Syndrome is a genetic condition inherited in an autosomal recessive pattern. This means an affected individual must inherit two copies of a mutated gene—one from each parent. The parents, who are typically "carriers," usually do not exhibit symptoms of the disease. To date, researchers have identified mutations in over 20 different genes (known as BBS genes) that can lead to Bardet-Biedl Syndrome. Genetic testing is highly recommended for families to confirm the diagnosis and provide accurate recurrence risk counseling.

How is Bardet-Biedl Syndrome different from other conditions?

While Bardet-Biedl Syndrome shares features with other ciliopathies like Alström syndrome or McKusick-Kaufman syndrome, it is clinically distinct. The presence of polydactyly and a specific pattern of retinal dystrophy often helps clinicians distinguish it from other rare diseases. Unlike some conditions that affect only one organ, the systemic involvement of the kidneys and metabolic system in Bardet-Biedl Syndrome requires a multidisciplinary medical approach.

Next steps

• Consult with a clinical geneticist to discuss genetic testing and family planning.


• Establish care with a multidisciplinary team including an ophthalmologist, nephrologist, and endocrinologist.


• Connect with the DiseaseMaps.org community to share resources with other families.


• Visit the Bardet-Biedl Syndrome Foundation website for the latest updates on clinical trials and research.

Medical Disclaimer: This information is for educational purposes only and does not constitute medical advice, diagnosis, or treatment; always seek the advice of your physician or other qualified health provider with any questions regarding a medical condition.

References

• NIH Genetic and Rare Diseases Information Center (GARD): Bardet-Biedl Syndrome.


• Orphanet: Portal for rare diseases and orphan drugs (ORPHA:110).


• OMIM (Online Mendelian Inheritance in Man): Entry #209900.


• Bardet-Biedl Syndrome Foundation (bbs-fc.org).