Study of 250 children with idiopathic mental retardation reveals nine cryptic and diverse subtelomeric chromosome anomalies

Authors

  • Elizabeth Baker,

    1. Centre for Medical Genetics, Department of Cytogenetics and Molecular Genetics, Women's and Children's Hospital, Adelaide, Australia
    2. Department of Paediatrics, University of Adelaide, Adelaide, Australia
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  • Lyn Hinton,

    1. Centre for Medical Genetics, Department of Cytogenetics and Molecular Genetics, Women's and Children's Hospital, Adelaide, Australia
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  • David F. Callen,

    1. Centre for Medical Genetics, Department of Cytogenetics and Molecular Genetics, Women's and Children's Hospital, Adelaide, Australia
    2. Department of Molecular Biosciences, University of Adelaide, Adelaide, Australia
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  • Meryl Altree,

    1. South Australian Clinical Genetics Service, Women's and Children's Hospital, Adelaide, Australia
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  • Angus Dobbie,

    1. South Australian Clinical Genetics Service, Women's and Children's Hospital, Adelaide, Australia
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  • Helen J. Eyre,

    1. Centre for Medical Genetics, Department of Cytogenetics and Molecular Genetics, Women's and Children's Hospital, Adelaide, Australia
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  • Grant R. Sutherland,

    1. Centre for Medical Genetics, Department of Cytogenetics and Molecular Genetics, Women's and Children's Hospital, Adelaide, Australia
    2. Department of Molecular Biosciences, University of Adelaide, Adelaide, Australia
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  • Elizabeth Thompson,

    1. South Australian Clinical Genetics Service, Women's and Children's Hospital, Adelaide, Australia
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  • Peter Thompson,

    1. University Hospital of Wales, Cardiff, Wales
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  • Erica Woollatt,

    1. Centre for Medical Genetics, Department of Cytogenetics and Molecular Genetics, Women's and Children's Hospital, Adelaide, Australia
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  • Eric Haan

    Corresponding author
    1. South Australian Clinical Genetics Service, Women's and Children's Hospital, Adelaide, Australia
    • South Australian Clinical Genetics Service, Women's and Children's Hospital, 72 King William Road, North Adelaide SA 5006, Australia.
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Abstract

Cryptic subtelomeric chromosome anomalies have been recognized as a significant cause of dysmorphology and mental retardation. To determine whether the clinical cytogenetics laboratory should screen routinely for these aberrations, we have tested 250 patients with idiopathic mental retardation/developmental delay, either isolated (53) or associated with dysmorphic features and/or malformations in the absence of a recognizable syndrome (197). All had normal karyotypes at the 550–850 band level. Subtelomeric anomalies were found in 1/53 of the first group (1.9%) and 8/197 of the second group (4.1%). In one patient, two separate anomalies were present: a deletion (not inherited) and a duplication (inherited). It is possible that one of these 10 observed aberrations might represent a rare and previously unreported polymorphism and one a rare cross-hybridization. Our study supports the proposition that cryptic subtelomeric rearrangements are a significant cause of idiopathic mental retardation/developmental delay, but both the diversity of the phenotypes of the positive cases and the wide diversity of their associated chromosome abnormalities emphasize the central problem for the clinical cytogenetics laboratory—that of choosing the most productive patient base for this useful diagnostic test. © 2002 Wiley-Liss, Inc.

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