Bardet–Biedl syndrome

Bardet–Biedl syndrome
Other names	Biedl-Bardet syndrome epigenetic phenomena also cause some of the variation seen in BBS.
Specialty	Medical genetics

Bardet–Biedl syndrome (BBS) is a

There is a wide range of secondary features that are sometimes associated with BBS[3]^{: 147–148} including^{[3]: 153–154}

• blindness caused by an impaired photoreceptor transport mechanism in the retina.^[4]
• "Brachydactyly, syndactyly of both the hands and feet is common, as is partial syndactyl (most usually between the second and third toes)"
• Polyuria/polydipsia (nephrogenic diabetes insipidus)
• Ataxia/poor coordination/imbalance
• Mild hypertonia (especially lower limbs)
• Diabetes mellitus
• Hepatic
  involvement
• Anosmia
• Auditory deficiencies
• bowel obstruction has been described.^[5]
• left ventricle and dilated cardiomyopathy
  .
• fallopian tubes
• Speech disorder/delay
• Developmental delay, especially of fine and gross motor skills^[citation needed]

Relation to other rare genetic disorders

Findings in genetic research published in 2006 have suggested that a large number of

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

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]}

A theory that photoreceptor cells are nourished by the IFT of retinal cilia now offers a potential explanation for the retinal dystrophy common in BBS patients after their early years of life.^[9][10]

Genes involved include:

• BBsome: BBS1, BBS2, ARL6/BBS3, BBS4, BBS5, BBS7, TTC8/BBS8, BBS10, TRIM32/BBS11 BBS12, CCDC28B, CEP290, TMEM67, MKS1, MKKS^[11]
• BBS6^{[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.

References