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Behavioural phenotype of Bardet-Biedl syndrome
  1. S Barnett1,
  2. S Reilly2,
  3. L Carr3,
  4. I Ojo4,
  5. P L Beales5,
  6. T Charman6
  1. 1Psychology Department, University College London, UK
  2. 2Faculty Health Sciences, LaTrobe University, Melbourne, Australia
  3. 3Neurosciences Unit, Institute of Child Health, London, UK
  4. 4St George’s Hospital Hornchurch, Essex, UK
  5. 5Molecular Medicine Unit, Institute of Child Health, London, UK
  6. 6Behavioural and Brain Sciences Unit, Institute of Child Health, London, UK
  1. Correspondence to:
 Dr T Charman, Behavioural and Brain Sciences Unit, Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK;

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Bardet-Biedl syndrome (BBS), also known as Laurence-Moon-Bardet-Biedl syndrome (LMBBS), has long been regarded as an autosomal recessive condition but recent evidence now points to a more complex pattern of inheritance.1–3 Prevalence rates range from 1 in 100 000 to 1 in 160 000,4–6 although there are communities in which BBS appears to be more common as a result of consanguinity.3,7 BBS is a heterogeneous genetic condition with six gene loci mapped to date: 11q13 (BBS1),8 16q21 (BBS2),9 3p12-13 (BBS3),10 15q23 (BBS4),11 2q31 (BBS5),12 and 20p12 (BBS6/MKKS).13,14 Three of these genes have now been identified, BBS2, BBS4, and BBS6.15 The phenotype of BBS varies from one family to another and within families, with only subtle phenotypic difference related to the different genes identified to date.16,17

The accepted major criteria for diagnosis include retinal dystrophy, obesity, polydactyly, male hypogonadism, mental retardation, and renal dysfunction.3 In addition to the primary features, a number of associated secondary features, including neurological, speech, and language deficits, behavioural traits, facial dysmorphism, and dental anomalies have been identified.18 The motor problems identified include delay in acquisition of motor skills, unsteady gait, and ataxia.18 Language development is delayed in many cases, although this may be commensurate with overall intellectual function, and there are also reports of speech problems that include articulation difficulties, consonant omission or distortions, dysarthria and hypernasality.3,4,17–19 Developmental delay has been widely described as a major feature of BBS, with two-thirds to three-quarters of patients performing in the mental retardation range on formal testing4,18,20 (but see Green et al3 for an exception).

Disturbances in behaviour have been reported in …

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