Bardet-Biedl syndrome

Laurence-Moon-Biedl syndrome and Laurence-Moon-Biedl-Bardet redirect here. See below for an explanation.

The Bardet-Biedl syndrome is a genetic disorder characterized mainly by obesity, pigmentary retinopathy, polydactyly, mental retardation, hypogonadism, and renal failure in some cases.^[1]

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Eponym and classification

The syndrome is named after Georges Bardet and Arthur Biedl.^[2]

Two forms have been identified:

• Bardet-Biedl syndrome 1 (BBS1) has no linkage to chromosome 16
• Bardet-Biedl syndrome 2 (BBS2) is mapped to markers on chromosome 16.

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 the syndrome. Laurence-Moon syndrome is usually considered a separate entity. However, some recent research suggests that the two conditions may not be distinct.^[3]

Major features

• Eyes: Pigmentary retinopathy, poor visual acuity, low vision, and/or blindness.
• Nose: Loss of, or reduced sense of, smell. (anosmia)
• Hand and foot: Polydactyly or syndactyly (webbing of fingers and toes).
• Cardiovascular system: Hypertrophy of interventricular septum and left ventricle and dilated cardiomyopathy.
• Gastrointestinal system: Fibrosis.
• Urogenital system: Hypogonadism, renal failure, urogenital sinuses, ectopic urethra, uterus duplex, septate vagina, and hypoplasia of the uterus, ovaries, and fallopian tubes.
• Growth and development: Mental and growth retardation.
• Behavior and performance: a wide variety of socialization and social interaction problems have been identified with BBS. Some refer to it as a kind of "mild-Autism." Many children who are later (explicitly and formally) diagnosed with the syndrome have gone through an extended period of time where school and medical professionals have struggled to find a name for the child's problems over several years.
• Heredity: The syndrome is familial and is transmitted as an autosomal recessive trait. chromosome 3 locus appears to be linked to polydactyly of all four limbs, whereas chromosome 15 is associated with early-onset morbid obesity and is mostly confined to the hands, and chromosome 16 represents the "leanest" form.
• Additional features: Obesity.

Cause

The detail biochemical mechanism that leads to BBS is still unclear. Recently, eight genes (BBS1 to BBS8) that are responsible for the disease when mutated have been cloned, and most of the gene products encoded by these BBS genes are located in the basal body and cilia of the cell. It has been postulated that these BBS gene products might involve in the cell signaling pathway in the cilia, and these signaling systems play an essential role in the normal development so that a malfunction in these systems causes the diverse pathological effects of the Syndrome.

In addition to so-called "signaling' along the cilia, it appears that Intraflagellar transport (IFT) of proteins along the cilia are essential for the formation and maintenance of healthy cells. In particular, abnormalities in retinal cilia are hypothesized to be related to the retinal dystrophy which is common in BBS patients.

June 2006 Conference

• The LMBBS Association Family Meeting for non-medical-professionals was held in Houston, Texas, June 16-17, 2006.

The conference was sponsored by a steering committee of BBS folk and parents/grandparents of children with BBS. It was directed to a lay audience.

A primary purpose of the conference was to present the latest medical research results in an accessible fashion. This included one morning of presentations by leading BBS genetic researchers Dr. Richard Lewis (Baylor Medical Center, Houston) and Dr. Nicholas Katsanis (Johns Hopkins University, Baltimore, Maryland). Several additional doctors presented accessible information on growth and weight management; kidney issues; obesity & Syndrome X; pediatric bariatric surgery; and speech pathology & therapy.

Location: Cullen Eye Institute, Baylor College of Medicine, Houston, Texas.

For additional information about the meeting, click here.

References

1. ^ Beales P, Elcioglu N, Woolf A, Parker D, Flinter F (1999). "New criteria for improved diagnosis of Bardet-Biedl syndrome: results of a population survey". J. Med. Genet. 36 (6): 437-46. PMID 10874630.
2. ^ synd/3745 at Who Named It
3. ^ Moore S, Green J, Fan Y et al (2005). "Clinical and genetic epidemiology of Bardet-Biedl syndrome in Newfoundland: a 22-year prospective, population-based, cohort study". Am. J. Med. Genet. A 132 (4): 352-60. PMID 15637713.