Bardet-Biedl Syndrome Details

Expanded Description

Bardet-Biedl Syndrome is a ciliopathic human genetic disorder that produces many effects and affects many body systems. Bardet-Biedl syndrome is an inherited condition that affects many parts of the body. People with this condition have progressive visual impairment due to cone-rod dystrophy, extra fingers or toes (polydactyly), truncal obesity, decreased function of the male gonads (hypogonadism), kidney abnormalities, and learning difficulties.


0.8 ( Per 100,000 Population ) [Source]


Bardet-Biedl syndrome can be caused by mutations in at least 14 different genes (often called BBS genes). They are known or are suspected to play critical roles in cell structures called cilia (microscopic, finger-like projections on the surface of many types of cells). They’re involved in cell movement and different chemical signaling pathways. They are also necessary for the perception of sensory input (e.g. sight, smell, hearing). The proteins produced from BBS genes are involved in the maintenance and function of cilia. Mutations lead to problems with cilia, which possibly disrupt important chemical signaling pathways during development and lead to abnormalities of sensory perception. About one-quarter of all cases of Bardet-Biedl syndrome result from mutations in the BBS1 gene. Another 20 percent of cases are caused by mutations in the BBS10 gene. The other BBS genes each account for only a small percentage of all cases of this condition. In about 25 percent of people with Bardet-Biedl syndrome, the cause of the disorder is unknown. Bardet-Biedl syndrome is typically inherited in an autosomal recessive pattern, which means both copies of a BBS gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Disorder Symptoms

Symptoms of Bardet-Biedl syndrome involves many parts of the body and can vary among affected individuals. One major feature is progressive vision loss due to the deterioration of the retina. This begins in mid-childhood with night vision problems followed by the development of blind spots in peripheral vision. These spots enlarge with time and eventually merge to produce tunnel vision. Most also develop blurred central vision and becomes blind by adolescence or early adulthood. Other symptoms include obesity (which can cause type 2 diabetes, high blood pressure, and abnormally high cholesterol levels), kidney abnormalities, the presence of extra fingers and/or toes (polydactyly), intellectual disability or learning problems, and abnormalities of the genitalia. Most affected males are infertile due to the reduced amounts of sex hormones produced. Other characteristics include impaired speech, delayed development of motor skills, poor coordination, and behavioural problems. In addition, some affected individuals have distinctive facial features, dental abnormalities, a partial or complete loss of the sense of smell, and unusually short or fused fingers and/or toes.

We don't have any symptoms yet.


Bardet-Biedl syndrome is usually diagnosed in childhood through clinical evaluation and detection of characteristic findings. Diagnosis of retinal disease can be made by an ophthalmologist after an examination and sometimes with the assistance of specialized tests, including an electroretinogram (ERG), a procedure that measures the electrical response of the retina to light stimulation.The differential diagnosis should include the Alström, McKusick-Kaufmann and Meckel-Gruber syndromes.

Diagnostic Tests

Diagnostic tests include genetic testing. However, such testing is currently only available through research laboratories with a special interesting in disease complex.

We don't have any tests yet.

Disorder Treatments

There is currently no cure for Bardet-Biedl syndrome. Treatment generally focuses on specific signs and symptoms that each individual has. Early evaluation by a specialist can help to provide vision aids and mobility training. The management of obesity may include education, diet, exercise, and behavioural therapies starting an early age. Complications of obesity, such as high cholesterol and diabetes mellitus are typically treated as they normally would be. Management of intellectual disability includes early intervention, special education and speech therapy as needed. Many affected adults are able to develop independent living skills. Although kidney transplants have been successful, the immunosuppressants used after a transplant may contribute to obesity. Affected individuals may undergo surgical correction of polydactyly (extra fingers and/or toes) and genital abnormalities. As children approach puberty, hormone levels should be monitored to determine if hormone replacement therapy is necessary.

We don't have any treatments yet.


The social lives of these patients will be affected by progressive vision loss due to retinal dystrophy, moderate intellectual deficit (when present), behavioral anomalies, hypomimia, and obesity.

Tips for Living with the Disorder

Name Description
Tip #1

The education of affected children should include planning for future blindness. In addition, diet and exercise (a healthy lifestyle) is needed to control obesity.

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