Bardet-Biedl syndrome 1

How is Bardet-Biedl syndrome inherited?

BBS has an autosomal recessive pattern of inheritance. This means that to have the syndrome, a person must have a mutation in both copies of the responsible gene in each cell. People with BBS inherit one mutated copy of the gene from each parent, who is referred to as a carrier. Carriers of an autosomal recessive condition typically do not have any signs or symptoms (they are unaffected). When 2 carriers of an autosomal recessive condition have children, each child has a:

  • 25% chance to be affected
  • 50% chance to be an unaffected carrier like each parent
  • 25% chance to be unaffected and not a carrier

Some cases of BBS (fewer than 10%) appear to require the presence of at least three mutations for a person to have features of the condition. This is known as triallelic inheritance. In these cases, in addition to inheriting a mutation in the same gene from each parent, a child also needs to have at least one more mutation in another gene to be affected.

Last updated on 05-01-20

Name: Bardet-Biedl Syndrome UK BBS UK 10 High Cross Road Roderston, Newport NP 10 9AD
United Kingdom
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Name: Bardet-Biedl Syndrome Foundation Url:

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The RareGuru disease database is regularly updated using data generously provided by GARD, the United States Genetic and Rare Disease Information Center.

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