Hypokalemic Periodic Paralysis (HypoPP) is a rare disease whereby voltage-gated ion channels are mutated and it is characterized by episodic flaccid paralysis concomitant to variations in blood potassium levels. Attacks usually happen after exercise or high carbohydrate meals. The diagnosis is made with laboratory data wich helps to exclude other causes and confirm low potassium serum or myotonia on eletromyography (EMG). The case report shows a patient who had severe symptoms of HypoPP and had laboratory data of low potassium serum during attacks and EMG with features more common in Hyperkalemic Periodic Paralysis. It also presented a great reponse to therapeutic treatment with potassium reposition and acetazolamide.