Spectrum of nondystrophic skeletal muscle channelopathies in children

Publication date: Available online 16 February 2017
Source:Pediatric Neurology
Author(s): Fouad Al-Ghamdi, Basil T. Darras, Partha S. Ghosh
BackgroundThe nondystrophic skeletal muscle channelopathies are a group of disorders caused by mutations of various voltage-gated ion channel genes. This includes nondystrophic myotonia (NDM) and periodic paralysis (PP).MethodsWe identified patients with a diagnosis of muscle channelopathy from our neuromuscular database in a tertiary care pediatric center from 2005-2015. We then performed retrospective review of their medical records for demographic characteristics, clinical features, investigations, treatment and follow-up.ResultsThirty-three patients were identified. Seventeen had nondystrophic myotonia. Seven of them had chloride channelopathy [Becker disease (4), Thomsen disease (3)]. Warm-up phenomenon and muscle hypertrophy were common clinical manifestations in this subgroup. Ten patients had sodium channelopathy [paramyotonia congenita (4) and other sodium channel myotonia (6)]. Stiffness of the facial muscles was an important presenting symptom and eyelid myotonia was a common clinical finding in this subgroup. The majority of these patients had electrical myotonia. Mexiletine was effective in controlling the symptoms in patients who had received treatment. Sixteen children had periodic paralysis [hyperkalemic PP (4), hypokalemic PP (8), Andersen-Tawil syndrome (4)]. Acetazolamide was commonly used to prevent paralytic attacks and was found to be effective.ConclusionsNondystrophic muscle channelopathies present with diverse clinical manifestations (myotonia, muscle hypertrophy, proximal weakness, swallowing difficulties and PP). Cardiac arrhythmias are potentially life-threatening in Andersen-Tawil syndrome. Timely identification of these disorders is helpful for effective symptomatic management and genetic counseling.



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