Paramyotonia congenita (PMC) is characterized by nondystrophic myotonia aggravated by exercise and cold exposure. SCN4A mutations manifest as various phenotypes of channelopathy, including PMC, myotonia congenita, and periodic paralysis. SCN4A-related channelopathy is characterized by autosomal dominant inheritance. Parental gonadal mosaicism is suspected in cases of recurrent de novo mutation in an autosomal dominantly inherited disease. We report a case of two Korean brothers presenting with PMC due to same de novo SCN4A point mutation, probably due to parental gonadal mosaicism.
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Kang et al. (2024) studied this question.
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