Open AccessPhenotypic heterogeneity in skeletal muscle sodium channelopathies: A case report and literature review
Author(s) -
Rabia Saleem,
Gururaj Setty,
Arif Khan,
D. Farrell,
Nahin Hussain
Publication year - 2013
Publication title -
journal of pediatric neurosciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.247
H-Index - 18
eISSN - 1998-3948
pISSN - 1817-1745
DOI - 10.4103/1817-1745.117848
Subject(s) - myotonia , myotonia congenita , medicine , channelopathy , sodium channel , periodic paralysis , electromyography , skeletal muscle , phenotype , genetic heterogeneity , muscle weakness , genetic testing , paralysis , bioinformatics , genetics , physical medicine and rehabilitation , gene , sodium , myotonic dystrophy , surgery , biology , chemistry , organic chemistry
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.