Hyperkalemic periodic paralysis and paramyotonia congenita caused by a de novo mutation in the SCN4A gene

ABSTRACT

Familial hyperkalemic periodic paralysis is an autosomal-dominant channelopathy characterized by reversible paralysis associated with episodic hyperkalemia. Mutations in the skeletal muscle voltage-gated sodium channel gene (SCN4A) have been reported to be responsible for this disorder. Paramyotonia congenita is also caused by mutations in the SCN4A gene. Here, we report the case of a 17-year-old boy who presented with both hyperkalemic periodic paralysis and paramyotonia congenita. A molecular analysis of the SCN4A gene revealed a heterozygous T>C transition at nucleotide 2078, leading to an Ile693Thr mutation. This mutation was absent in the patient’s parents supporting a de novo Ile693Thr mutation in our patient.