Titre :
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Autosomal recessive myotonia congenita : clinical, electrophysiological and genetic study in 6 families : Actes de colloque : Congrès international de myologie 2008 (International Congress of Myology 2008) 26-30 mai 2008 - Marseille
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contenu dans :
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Auteurs :
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Belaidi H ;
Regragui W ;
Kably B ;
Urtizberea JA ;
Ouazzani R
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Type de document :
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Article
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Année de publication :
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2008
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Pages :
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p. 595
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Langues:
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Anglais
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Mots-clés :
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muscle orbiculaire de l'oeil
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Résumé :
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Myotonia congenita (MC) can be Autosomal recessive (Becker) or Autosomal dominant (Thomsen). These 2 forms are due to mutations in CLCN1 gene coding for chloride channel of muscle membrane. This is a study of the clinical and electrophysiological phenotypic features and genetic data in 6 Moroccan families. Twelve patients with Becker MC had clinical evaluation for age at onset, myotonia distribution, muscle hypertrophy and weakness and electrophysiological examination for the pattern of chloride channelopathy. Family investigation consisted of clinical and electrophysiological examination of at risk relatives. Molecular analysis was performed in one family. Age at onset ranged from 2 and 10 years. Myotonia was the predominant symptom that improved by exercise in all cases and worsened by cold in 5 patients. It was noticed in orbicularis oculi muscles in 5 cases. Eight patients had moderate weakness in limb girdle muscles. Muscle hypertrophy was a constant sign. All patients had myotonic discharges at needle EMG examination. The effort test and repetitive stimulation showed typical patterns in 4 cases. Autosomal recessive inheritance was confirmed by established consanguinity and normal clinical and electrophysiologic examination of the parents in all families. An homozygous mutation in the CLCN1 gene was demonstrated in one patient. Functional disability was moderate in all cases due mostly to myotonia which responded partially to symptomatic treatment. Becker MC has homogeneous phenotype. The clinical signs are explained by loss of function in the chloride channel responsible of muscle membrane hyperpolarisation.
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