Familial hypokalemic periodic paralysis is an autosomal-dominant channelopathy characterized by episodic muscle weakness with hypokalemia. The respiratory and cardiac muscles typically remain unaffected, but we report an atypical case of a family with hypokalemic periodic paralysis in which the affected members presented with frequent respiratory insufficiency during severe attacks. Molecular analysis revealed a heterozygous c.664 C>T transition in the sodium...