[A family with heat-sensitive myotonia alternating with hypokalemic periodic paralysis].

We report a 34-year-old man with evident family history of paralysis and myotonia. He has noticed episodic morning paralysis alternating with muscle myotonia since the age of 10 years. When an episode of paralysis occurred, his serum potassium level decreased to 2.3 mEq/L and tended to increase to about 4.0 mEq/L when he complained myotonia. This case is obviously different from several already-known diseases, as it is perhaps the first case thermo-sensitive disorder of muscle activity in that the myotonia is induced by warm environment but paralysis occurs in the setting of cold ambient temperature and hypokalemia. Therefore, we are underway to perform molecular genetic analysis of ion channels since paramyotonia/hyperkalemic periodic paralysis is known to be associated with Na(+)-channel missense mutations, while hypokalemic periodic paralysis is with Ca(++)-channel. Addendum: After submission of the manuscript, we identified a novel mutation in Na+ channel alpha subunit. The detail of molecular aspect will be reported elsewhere.