Variants of the skeletal muscle sodium channel gene SCN4A are associated with different neuromuscular disorders including sodium channel myotonia. Here, we report an infant with a de novo variant in SCN4A presenting with neonatal onset of severe muscle stiffness with involvement of facial and eyelid muscles, and life-threatening events with respiratory failure due to severe apnoea and thorax rigidity. The boy dramatically improved in both respiratory and motor function under carbamazepine therapy.
Keywords: Muscle stiffness; Myotonia; Respiratory failure; SCN4A.
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