the periodic hyperpotassemia paralysis is a striated muscle channelopathy characterized by recurrent episodes of muscular asthenia that may to be triggered by exercise, cold, not rest after exercise and potassium support. this the case of a female patient aged 13 diagnosed with hyperpotassemia periodic paralysis without family backgrounds of this entity and also without associated myotonia. the seizures of muscular asthenia occurred almost daily and each 2 or 3 days with a variable length from a half hour to 24 to 48 hours. during a episode of muscular asthenia there were blood potassium concentrations of 7,14 mmol/l and the electromyogram showed a myopathic pattern. there was a frequency decrease of episodes of muscular asthenia at 2 months of treatment onset with oral acetazolamide.