A case of hypokalemic periodic paralysis: Utility of exercise test for the assessment of therapeutic efficacy

We report a 14-year-old male with hypokalemic periodic paralysis. He noticed periodic paralysis at the age of 11. Any complication did not accompany the symptom. At the age of 12, hypokalemia was found during an episode of paralysis, and he was diagnosed as hypokalemic periodic paralysis. The frequency of paralytic attack increased around April 2000. Although long-acting oral potassium (32 mEq/day) was administered, it did not give favorable effect. Therapeutic spironolactone trial also failed. After the reconfirmation of the diagnosis of periodic paralysis by an exercise test, oral acetazolamide (750 mg/day) was started. In subsequent exercise test, the increment of the CMAP amplitude of abductor digiti minimi during exercise became smaller and the decrement of CMAP amplitude after exercise disappeared thereafter, which was assumed to be related with clinical improvement. The noninvasive exercise test is useful not only to diagnose periodic paralysis but also to evaluate therapeutic efficacy.