Bardet-Biedl syndrome causes

Written by Lila Levinson, PhD | Last updated May 18, 2026
Fact-checked by Lindsey Shapiro, PhD

Jump to:

• Causes
• Inheritance
• Why cause matters
• Pregnancy and BBS risk

Genetic mutations cause Bardet-Biedl syndrome (BBS), a rare condition associated with obesity and a range of other symptoms.

These mutations, which are usually inherited, cause problems with important cellular structures called cilia. For that reason, BBS is referred to as a ciliopathy, a group of genetic disorders characterized by cilia defects.

Understanding BBS genetics is often important for diagnosis, and may play a role in family planning for people with BBS and their relatives. Genetic results may also help care teams prioritize symptom monitoring and treatment.

What causes Bardet-Biedl syndrome?

The genetic causes of BBS  vary between individuals — researchers have linked at least 28 genes to the disease. That said, some of the genes most commonly linked to BBS include:

• BBS1
• BBS10
• BBS2
• BBS12

Certain gene mutations are more common among different racial and ethnic groups. BBS1 and BBS10 are the most frequently implicated genes globally.

All BBS gene mutations ultimately disrupt cilia, the tiny hairlike structures found on the surface of many cells. Cilia serve several purposes, helping move fluid or cells, and enabling cells to sense what’s going on around them. In BBS, sensory cilia are most affected.

Many genes associated with BBS are involved in the formation of the BBSome, a protein complex that’s needed for proper cilia function. For example, BBS1 and BBS2 contain the genetic code for proteins that make up the BBSome, while BBS10 and BBS12 encode proteins that help the BBSome assemble.

Mutations in these genes ultimately lead to cilia dysfunction, which, in turn, causes a wide range of issues with cell signaling and other vital processes.

How genetic mutations affect symptoms

Ciliopathy disrupts biological processes throughout life:

• Cilia play important roles during fetal development, including in the formation of limbs and other organs. Babies with BBS may be born with extra toes or fingers, called polydactyly, as well as malformations of the genitals or urinary tract.
• Young children with BBS often develop kidney problems and obesity, which are thought to be linked to cell signaling problems caused by cilia defects in kidney and nerve cells.
• Specialized cilia help the eyes sense light, so people with BBS often develop vision problems during childhood, which may worsen later in life. Learning disabilities also often become apparent during childhood, which may be related to cilia dysfunction in nerve cells.

Some studies suggest that mutations in certain genes correlate with specific BBS symptom profiles. For example, mutations in BBS10 have been linked to severe kidney problems and significant obesity, while BBS1 tends to have a milder disease course. However, symptoms can vary even for people with the same mutations.

How is Bardet-Biedl syndrome inherited?

BBS typically follows an autosomal recessive inheritance pattern, meaning that a person needs two mutated copies of a gene — one from each biological parent — to develop the disease. BBS carriers, or people with one mutated and one unmutated copy, can pass mutations to their biological children, but don’t usually develop symptoms.

The inheritance risk of BBS is the same for males and females.

These patterns apply when parents have mutations in the same BBS-causing gene. BBS inheritance may become more complicated if both parents carry BBS-causing mutations, but the mutations are in different genes.

It is possible for BBS to arise from new, or de novo mutations that occur spontaneously and are not passed down in families. However, de novo cases of recessive genetic conditions like BBS are rare.

Why knowing the cause matters

Understanding the causes of BBS has implications for diagnosis, care, and family planning.

Although BBS diagnosis relies largely on identifying characteristic symptoms, genetic testing is increasingly playing a role, helping to confirm the diagnosis in as many as about 80% of cases.

Knowing which mutations a person has may help doctors and patients decide on priorities for monitoring and care. In the future, if gene therapies and other targeted treatments for BBS become available, the genetic profile could also influence treatment options.

Because BBS is an inherited genetic disorder, understanding its cause informs family planning decisions for patients and their family members. Doctors may recommend that relatives of a diagnosed person undergo genetic testing to determine their carrier status. Genetic counseling for BBS can help patients and families understand inheritance risks, genetic testing results, and family planning options.

Is Bardet-Biedl syndrome caused by anything during pregnancy?

BBS is a strictly genetic condition. Individual choices — by patients themselves or by their parents during pregnancy — can’t cause the disease. Factors that cannot cause BBS include:

• diet
• lifestyle choices
• injury
• exposure to toxins or other environmental factors
• infection

Some of these may affect symptoms later in life, but none can cause BBS in the absence of genetic mutations.

Patients and parents who struggle with feelings of guilt about a BBS diagnosis may benefit from talk therapy or connecting with others in the BBS or rare disease communities.

Rare Obesity News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.