Bardet-Biedl Syndrome

What is Bardet-Biedl syndrome?

Bardet-Biedl syndrome is a rare disorder that affects many systems of the body but is primarily characterized by the deterioration of cells that receive light (i.e. cone and rod cells) and in the retina, an extra finger or toe, truncal obesity, renal abnormalities, and learning difficulties. Bardet-Biedl syndrome shows significant overlap with Laurence-Moon syndrome, and these conditions, now distinguished, were once thought to be the same.

What causes Bardet-Biedl syndrome?

Most cases of Bardet-Biedl syndrome are caused by a mutated gene and inherited in an autosomal recessive pattern. The most common gene mutation associated with Bardet-Biedl syndrome is on the BBS1 gene, but researchers have determined 12 separate genes that have been known to cause cases of the disease and still more are yet to be discovered. All of these genes are associated with cilia, which are the hair-like structures that cover almost all of the types of cells in the body. These cilia, specifically immotile ones, are responsibility for normal health and development, and many of the current symptoms from Bardet-Biedl syndrome can be attributed to the dysfunction of these cilia.

What are the symptoms of Bardet-Biedl syndrome?

The specific signs and symptoms of Bardet-Biedl syndrome, as well as their severity, varies greatly between individual patients. Visual impairment is one of the most characteristic symptoms of the condition, and it progresses (worsens) throughout the patient’s life, amounting to tunnel vision, nightblindness, or even complete vision loss. Additional vision abnormalities include crossed eyes, rapid eye movements, cataracts, and glaucoma. Along with an additional finger or toe near the fifth digit, webbing of the fingers or toes, abnormally short digits, and short, wide, and flat feet may also occur in patients. Other associated symptoms of Bardet-Biedl syndrome include the following:

• Delayed puberty or problems with development of the sex organs in both males and females
• Delays in speaking or speech impairment
• Behavioral problems, such as anxiety, depression, and OCD
• High blood pressure
• Abnormal gait
• Loss of the ability to smell
• Ataxia

How is Bardet-Biedl syndrome diagnosed?

Bardet-Biedl syndrome is usually able to be diagnosed in childhood after a clinical evaluation and a detection of the characteristic findings of the disease. In some cases, molecular genetic testing can help confirm a diagnosis.

What are the available treatments for Bardet-Biedl syndrome?

There is currently no cure for Bardet-Biedl syndrome, so treatment is symptomatic and supportive. Sometimes, surgery can correct any abnormalities of the fingers and/or toes or any congenital heart defects. Age-appropriate diets and exercise plans can help manage obesity in patients. The other complications of the disease need to be screened and managed by specialists.

Where can I find more information on Bardet-Biedl syndrome?

• National Organization for Rare Disorders (NORD)
• Bardet-Biedl Syndrome Family Association
• U.S. National Library of Medicine