| CASE REPORT |
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| Year : 2013 | Volume
: 8
| Issue : 2 | Page : 138-140 |
Phenotypic heterogeneity in skeletal muscle sodium channelopathies: A case report and literature review
Rashid Saleem1, Gururaj Setty1, Arif Khan1, Duncan Farrell2, Nahin Hussain1
1 Department of Paediatric Neurology, Leicester Royal Infirmary, University Hospitals of Leicester NHS Trust, Leicester, United Kingdom
2 Department of Neurophysiology, Leicester Royal Infirmary, University Hospitals of Leicester NHS Trust, Leicester, United Kingdom
Correspondence Address:
Rashid Saleem
Department of Paediatric Neurology, Leicester Royal Infirmary, Infirmary Road, Leicester - LE1 5WW
United Kingdom
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/1817-1745.117848
Skeletal muscle sodium channelopathies (SMSCs) including hyperkalemic periodic paralysis (HyperPP), paramyotonia congenita (PC), and sodium channel myotonia are caused by sodium channel gene (SCN4A) mutations, with altered sarcolemal excitability, and can present as episodes of skeletal muscle weakness, paralysis, and myotonia. We report a teenage boy, who presented with features of HyperPP, PC, myotonia congenita, and sodium channel myotonia. His electromyography (EMG) revealed myopathic changes, myotonia, and Fournier EMG pattern I, and posed a diagnostic challenge. Genetic analysis showed Thr704Met mutation in SCN4A gene. While with typical clinical phenotypes, the electromyographic patterns can be used to direct genetic testing, atypical phenotypes may pose diagnostic dilemmas. Clinicians dealing with neuromuscular disorders in children need to be aware of the unusual clinical presentations of SMSC, so that focused genetic testing can be carried out.
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