PT - JOURNAL ARTICLE AU - Khalid A. Alhasan AU - Mohammed S. Abdallah AU - Jameela A. Kari AU - Fahad A. Bashiri TI - Hypokalemic periodic paralysis due to <em>CACNA1S</em> gene mutation AID - 10.17712/nsj.2018.3.20180005 DP - 2019 Jul 01 TA - Neurosciences Journal PG - 225--230 VI - 24 IP - 3 4099 - http://nsj.org.sa/content/24/3/225.short 4100 - http://nsj.org.sa/content/24/3/225.full SO - Neurosciences (Riyadh)2019 Jul 01; 24 AB - Hypokalemic periodic paralysis (HypoPP) is a relatively rare but treatable disorder caused by mutations in the CACNA1S gene. HypoPP patients may experience paralytic episodes associated with hypokalemia and, infrequently, may develop late-onset proximal myopathy. The paralytic attacks are characterized by reversible flaccid paralysis and, in most cases, spare the respiratory muscles and heart. We report a case of CACNA1S periodic paralysis precipitated by vigorous exercise in a 14-year-old boy who presented with sudden-onset paralysis of both his upper and lower extremities. Laboratory evaluation revealed a markedly low serum potassium level. The patient’s symptoms resolved after correction of the potassium abnormality, and he was discharged with no neurological deficits. Although rare, HypoPP must be differentiated from other causes of weakness and paralysis so that proper treatment can be promptly initiated to ensure good outcomes.