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Handbook of Genetic Counseling/Bardet-Biedl Syndrome-2

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Bardet-Biedl Syndrome

Genetic Etiology

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  • Mode of inheritance: Autosomal Recessive. It requires a recessive mutation in one of six loci plus an additional mutation in a second locus, known as triallelic inheritance.
  • Chromosome locations: This syndrome is linked to 6 different loci-BBS1 on 11q13, BBS2 on 16q21, BBS3 on 3p13, BBS4 on 15q22.3, BBS5 on 2q31, and BBS6 on 20p12

Incidence and Carrier Frequency

  • Incidence is 1 in 100,000, with an increased prevalence in Arab and Bedouin populations (1 in 13,500). Carrier frequency is 1 in 179.

Clinical Features

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  • Obesity
  • Eye Problems: Rod-cone dystrophy (major)
    • Retinitis pigmentosa
    • Strabismus
    • Cataracts
  • Mouth and Tooth Problems: High arched palate
    • Dental crowding
    • Hypodontia
    • Small tooth roots
  • Cardiac Problems: Left ventricular hypertrophy
    • Other congenital heart defects
    • Hypertension
  • Hepatic Fibrosis
  • Hirschsprung disease (less than 10% of patients)
  • Hypogonadism (major)
  • Undescended testes (10%)
  • Hypothyroidism
  • Asthma (27%)
  • Renal Problems (major): Nephrogenic diabetes insipidus
    • Irregular kidney contour (fetal lobulation)
    • Polydipsia and Polyuria (66% of patients)
    • Recurrent urinary tract infections (30% of patients)
  • Polydactyly of hands and/or feet (major)
  • Brachydactyly of hands
  • Speech delays
  • Ataxia
  • Developmental delay
  • Learning disabilities (major)
  • Diabetes mellitus (15-45% of patients)
  • A clinical diagnosis is made with the presence of 4 major features or 3 major and 2 minor features
  • Age of onset is usually early childhood.
  • Life span is variable, depending on severity and management of symptoms.

Testing

  • Chromosomal testing is available. This can be done prenatally as well as postnatally.

Surveillance, Management, and Treatment Options

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  • In the clinic, fundoscopic examination of the eyes should be performed through dilated pupils as well as blood pressure measurement and urinalysis for glucose, protein and leukocytes. Baseline investigations should include ERG/VER, ECG, echocardiogram, ultrasound of the kidneys and urinary tract and either an IVP or DMSA/DPTA scan. The child should be evaluated by cardiology, ophthalmology, urology, nephrology, genetics, speech, endocrinology, and orthopedics. It is not possible to cure this condition, but regular follow-up for symptoms can improve quality of life.

Psychosocial Issues

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  • Guilt, fear, anger, anxiety, sadness, desperation, and depression are common feelings associated with this diagnosis. It is important to assess the family situation, support system, financial position, and living environment as well as offer any resources to families that may be helpful

Support Groups

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  • Retinitis Pigmentosa International
23241 Ventura Boulevard
Woodland Hills CA 91364
8189920500
8003444877
e-mail: rpint@pacbell.net
Home Page: [1]
  • American Foundation for the Blind
11 Penn Plaza
New York NY 10001
2125027600
8002325463
e-mail: afbinfo@afb.org
Home Page: [2]
  • American Printing House for the Blind
1839 Frankfort Avenue
Louisville KY 40206-0085
5028952405
8002231839
e-mail: info@aph.org
Home Page: [3]
  • National Association for Parents of the Visually Impaired
P.O. Box 317
Watertown MA 02472
6179727441
8005626265
e-mail: napvi@perkins.pvt.k12.ma.us
Home Page: [4]
  • Prevent Blindness America
500 East Remington Road
Schaumberg IL 60173
8478432020
8003312020
e-mail: info@preventblindness.org
Home Page: [5]
  • Vision Community Services
23 A Elm St
Watertown MA 02472
6179264232
8008523029
e-mail: mablind@tiac.net
Home Page: [6]
  • Blind Children's Fund
4740 Okemos Road
Okemos MI 48864-1637
5173471357
n/a
e-mail: blindchfnd@aol.com
Home Page: [7]
  • Laurence Moon Bardet Biedl Syndrome
c/o The Foundation Fighting Blindness
Hunt Valley MD 21031
4107851414
8883943937
e-mail: randerson@blindness.org
Home Page: [8]
  • American Council of the Blind, Inc.
1155 15th Street
Washington DC 20005
2024675081
8004248666
e-mail: info@acb.org
Home Page: [9]
  • National Association for Visually Handicapped
22 West 21st Street
New York NY 10010
2128893141
n/a
e-mail: staff@navh.org
Home Page: [10]
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