This condition is often inherited via autosomal recessive manner (including digenic recessive); but
epigenetic phenomena also cause some of the variation seen in BBS.
Bardet–Biedl syndrome is a
pleiotropic disorder with variable
expressivity and a wide range of clinical variability observed both within and between families. The most common clinical features are rod–cone
dystrophy, with childhood-onset night-blindness followed by increasing visual loss; postaxial
polydactyly;
truncalobesity that manifests during infancy and remains problematic throughout adulthood; varying degrees of learning disabilities; male
hypogenitalism and complex female
genitourinary malformations; and
renal dysfunction, a major cause of morbidity and mortality.
There is a wide range of secondary features that are sometimes associated with BBS[3]: 147–148 including[3]: 153–154
The detailed biochemical mechanism that leads to BBS is still unclear.[citation needed]
The gene products encoded by these BBS genes, called BBS proteins, are located in the
basal body and
cilia of the
cell.[7]
Using the round worm C. elegans as a model system, biologists found that BBS proteins are involved in a process called
intraflagellar transport (IFT), a bi-directional transportation activity within the cilia along the long axis of the ciliary shaft that is essential for
ciliogenesis and the maintenance of cilia.[8] Recent biochemical analysis of human BBS proteins revealed that BBS proteins are assembled into a multiple protein complex, called "BBSome". BBSome is proposed to be responsible for transporting intracellular vesicles to the base of the cilia and to play an important role in the ciliary function.[citation needed]
Since abnormalities of cilia are known to be related to a wide range of disease symptoms including those commonly seen in BBS patients, it is now widely accepted that mutated BBS genes affect normal cilia function, which, in turn, causes BBS.[citation needed]
The diagnosis of BBS is established by clinical findings and family history. Molecular genetic testing can be used to confirm the diagnosis. Multigene panels offer the most effective approach in achieving molecular confirmation of BBS.[citation needed]
Management
There is currently no specific treatment but it is important that an experienced multidisciplinary team manages patients with adequate supportive treatments.[12]
Eponym
The syndrome is named after
Georges Bardet and
Arthur Biedl.[13][why?] The first known case was reported by Laurence and Moon in 1866 at the Ophthalmic Hospital in South London. Laurence–Moon–Biedl–Bardet syndrome is no longer considered as valid terms in that patients of Laurence and Moon had
paraplegia but no polydactyly or obesity, which are the key elements of the Bardet–Biedl syndrome.
Laurence–Moon syndrome is usually considered a separate entity. However, some recent research suggests that the two conditions may not be distinct.[14]
As of 2012[update], 14[11]
(or 15)[15] different BBS genes had been identified.
^
ab
Hamosh A (2012-11-02).
"OMIM entry #209900 Bardet-Biedl Syndrome; BBS". Online Mendelian Inheritance in Man. McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine. Archived from
the original on 2016-05-17. Retrieved 2013-09-04.