Bardet-Biedl Syndrome 9

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2019-09-22
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A number sign (#) is used with this entry because Bardet-Biedl syndrome-9 (BBS9) is caused by homozygosity or compound heterozygosity for mutations in the PTHB1 gene (607968) on chromosome 7p14.

Description

BBS9 is an autosomal recessive disorder characterized by obesity, polydactyly, renal anomalies, retinopathy, and mental retardation (Abu-Safieh et al., 2012).

For a general phenotypic description and a discussion of genetic heterogeneity of Bardet-Biedl syndrome, see BBS1 (209900).

Clinical Features

Abu-Safieh et al. (2012) reported 3 sibs with BBS9 from a consanguineous Arab family. One sib had most of the major features of the disorder, including obesity, mental retardation, renal disease, polydactyly, and retinitis pigmentosa, but the other 2 sibs had only retinitis pigmentosa with no additional features. The findings indicated an unusually high degree of intrafamilial variability in BBS.

Molecular Genetics

Nishimura et al. (2005) detected homozygosity for a mutation at the splice donor site of intron 17 of the PTHB1 gene (607968.0001) in the proband of a consanguineous Arab family. Screening of 95 unrelated BBS probands detected 5 probands with a homozygous mutation in PTHB1 and 1 proband with compound heterozygous mutations.

In 3 sibs, 1 with the major features of BBS and 2 with retinitis pigmentosa only, Abu-Safieh et al. (2012) found homozygosity for a frameshift mutation in the PTHB1 gene (607968.0008).