A fatal hyperthermic syndrome in a patient with myokymia

A fatal hyperthermic syndrome occurred in a patient with myokymia. The pati ent suffered acute circulatory collapse and severe rhabdomyolysis associate d with hyperthermia. Although these symptoms were similar to neuroleptic ma lignant syndrome or malignant hyperthermia, he did not have a history of an tipsychotic medication or anesthesia. Continuous muscular contraction due t o myokymia likely led to the development of hyperthermic syndrome.