Bardet-Biedl syndrome

Bardet-Biedl syndrome (BBS) is an inherited disorder that affects various parts of the body. Individuals affected by BBS typically have vision loss, obesity, extra digits, kidney disease, intellectual disability or learning difficulties, and abnormalities of the genitalia. The onset and symptoms can vary among affected individuals. Typically, night blindness occurs around 7 to 8 years and progresses to blindness in adolescence or early adulthood. Kidney disease can progress to renal failure, which has a significant effect on life expectancy. There is no specific treatment available but medical surveillance and care may help to improve some symptoms and overall condition of life. BBS is caused by pathogenic variants in 14 different genes, often collectively called the BBS genes.

BBS is inherited in an autosomal recessive manner. This type of inheritance requires the presence of two copies of a mutation in the gene for a person to have the genetic disease. Both parents must be carriers of a mutation in the gene in order to be at risk to have an affected child. The child must inherit a mutation from each carrier parent in order to be affected. There is a 1 in 4 chance that a baby will inherit two mutated copies of the gene and be affected when both parents are carriers.

There are no signs or symptoms associated with being a carrier for BBS. However, the risk to have a child affected with BBS is increased. Testing of reproductive partners is recommended for carriers of BBS.

BBS affects all ethnicities but it is more common among the Bedouin peoples of Kuwait where 1 in 13,500 newborns are affected and among the individuals from the island of Newfoundland, with 1 in 17,000 newborns affected. In the general population, BBS occurs in about 1 in 100,000 to 1 in 160,000 newborns.

The following websites may be informative: Genetics Home Reference: Bardet-Biedl syndrome (BBS) (http://ghr.nlm.nih.gov/)($)The National Organization for Rare Disorders (NORD): (https://www.rarediseases.org/)

OMIM [Bardet-Biedl syndrome (BBS): 209900] (http://www.ncbi.nlm.nih.gov/omim) Gene Reviews: Bardet-Biedl syndrome (BBS) (http://www.ncbi.nlm.nih.gov/books/NBK1116/)

• Full gene sequencing