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Thomsen or Becker myotonia? A novel autosomal recessive nonsense mutation in the CLCN1 gene associated with a mild phenotype

Authors

  • Juliana Gurgel-Giannetti MD, PhD,

    1. Centro de Estudos do Genoma Humano–IB-USP, Biosciences Institute, University of São Paulo, R. do Matão, 277, Sala 220, CEP 05508-900 São Paulo, Brazil
    2. Pediatrics Department, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
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  • Adriano S. Senkevics BSc,

    1. Centro de Estudos do Genoma Humano–IB-USP, Biosciences Institute, University of São Paulo, R. do Matão, 277, Sala 220, CEP 05508-900 São Paulo, Brazil
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  • Dinorah Zilbersztajn-Gotlieb BSc,

    1. Centro de Estudos do Genoma Humano–IB-USP, Biosciences Institute, University of São Paulo, R. do Matão, 277, Sala 220, CEP 05508-900 São Paulo, Brazil
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  • Lydia U. Yamamoto PhD,

    1. Centro de Estudos do Genoma Humano–IB-USP, Biosciences Institute, University of São Paulo, R. do Matão, 277, Sala 220, CEP 05508-900 São Paulo, Brazil
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  • Viviane P. Muniz MS,

    1. Centro de Estudos do Genoma Humano–IB-USP, Biosciences Institute, University of São Paulo, R. do Matão, 277, Sala 220, CEP 05508-900 São Paulo, Brazil
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  • Rita C.M. Pavanello MD,

    1. Centro de Estudos do Genoma Humano–IB-USP, Biosciences Institute, University of São Paulo, R. do Matão, 277, Sala 220, CEP 05508-900 São Paulo, Brazil
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  • Acary B. Oliveira MD, PhD,

    1. Department of Neurology, Universidade Federal de São Paulo, São Paulo, Brazil
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  • Mayana ZATZ PhD,

    1. Centro de Estudos do Genoma Humano–IB-USP, Biosciences Institute, University of São Paulo, R. do Matão, 277, Sala 220, CEP 05508-900 São Paulo, Brazil
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  • Mariz Vainzof PhD

    Corresponding author
    1. Centro de Estudos do Genoma Humano–IB-USP, Biosciences Institute, University of São Paulo, R. do Matão, 277, Sala 220, CEP 05508-900 São Paulo, Brazil
    • Centro de Estudos do Genoma Humano–IB-USP, Biosciences Institute, University of São Paulo, R. do Matão, 277, Sala 220, CEP 05508-900 São Paulo, Brazil
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Abstract

We describe a large Brazilian consanguineous kindred with 3 clinically affected patients with a Thomsen myotonia phenotype. They carry a novel homozygous nonsense mutation in the CLCN1 gene (K248X). None of the 6 heterozygote carriers show any sign of myotonia on clinical evaluation or electromyography. These findings confirm the autosomal recessive inheritance of the novel mutation in this family, as well as the occurrence of phenotypic variability in the autosomal recessive forms of myotonia. Muscle Nerve, 2012

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