RT Journal Article SR Electronic T1 Hypokalemic periodic paralysis due to CACNA1S gene mutation JF Neurosciences Journal JO Neurosciences (Riyadh) FD Prince Sultan Military Medical City SP 225 OP 230 DO 10.17712/nsj.2018.3.20180005 VO 24 IS 3 A1 Khalid A. Alhasan A1 Mohammed S. Abdallah A1 Jameela A. Kari A1 Fahad A. Bashiri YR 2019 UL http://nsj.org.sa/content/24/3/225.abstract 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.