Bardet-biedl syndrome

Laurence-Moon-Biedl syndrome and Laurence-Moon-Biedl-Bardet redirect here. See below for an explanation.
Not to be confused with Laurence–Moon syndrome.
Bardet–Biedl syndrome
Classification and external resources
ICD-10 9 OMIM DiseasesDB MeSH D020788

The Bardet–Biedl syndrome (BBS) is a ciliopathic human genetic disorder that produces many effects and affects many body systems. It is characterized principally by obesity, retinitis pigmentosa, polydactyly, hypogonadism, and renal failure in some cases.[1] Historically, mental retardation has been considered a principal symptom but is now not regarded as such.

Summary of the syndrome

Bardet–Biedl syndrome is a pleiotropic disorder with variable expressivity and a wide range of clinical variability observed both within and between families. The main clinical features are rod–cone dystrophy, with childhood-onset visual loss preceded by night blindness; postaxial polydactyly; truncal obesity that manifests during infancy and remains problematic throughout adulthood; specific learning difficulties in some but not all individuals; 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[2] including[3]

Eponym and classification

The syndrome is named after Georges Bardet and Arthur Biedl.[4]

The first known case was reported by Laurence and Moon in 1866 at the Ophthalmic Hospital in South London. Laurence–Moon–Biedl–Bardet syndrome are no longer considered as valid terms in that patients of Laurence and Moon had paraplegia but no polydactyly and 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.[5]

As of 2012, 14[6] (or 15)[7] different BBS genes have been identified.

Major clinical features

Pathophysiology

The detailed biochemical mechanism that leads to BBS is still unclear.

The gene products encoded by these BBS genes, called BBS proteins, are located in the basal body and cilia of the cell.[12]

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.[13] 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.

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 functions, which, in turns, causes BBS.

Genes involved include:

Relation to other rare genetic disorders

Recent findings in genetic research have suggested that a large number of genetic disorders, both genetic syndromes and genetic diseases, that were not previously identified in the medical literature as related, may be, in fact, highly related in the genetypical root cause of the widely-varying, phenotypically-observed disorders. BBS is one such syndrome that has now been identified to be caused by defects in the cellular ciliary structure. Thus, BBS is a ciliopathy. Other known ciliopathies include primary ciliary dyskinesia, polycystic kidney and liver disease, nephronophthisis, Alstrom syndrome, Meckel–Gruber syndrome and some forms of retinal degeneration.[14]

References

External links

  • Laurence Moon Bardet Biedl Society (UK-based)
  • LMBBS Association a US-based association promoting awareness of BBS
  • basal bodies in many organ systems of human physiology. Includes multiple specific mentions of BBS.
  • Johns Hopkins University
  • United States National Library of Medicine
  • Foundation Fighting Blindness
  • Bardet–Biedl Syndrome Association francaise (France-based; in French language) Syndrome de Bardet-Biedl (BBS)
  • Bardet–Biedl syndrome at GeneReview/UW/NIH

Template:Other genetic disorders by mechanism Template:Deficiencies of intracellular signaling peptides and proteins

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