The periodic paralyses are a group of autosomal-dominant disorders of skeletal muscle sodium, potassium, and calcium channel genes. They are characterized by episodes of muscle weakness associated with variations in serum potassium concentration. Hyperkalemic periodic paralysis (HYPP) is caused by gain-of-function mutations in the alpha-subunit of the skeletal muscle voltage-gated sodium channel, Nav1.4. However, 20% of cases remain genetically undefined, suggesting genetic heterogeneity. HYPP is characterized by attacks of flaccid limb paralysis or, rarely, weakness of the eye and throat muscles. Triggers for these attacks include ingestion of potassium-rich food, rest after strenuous exercise, and cold exposure.
