Hyperthermia, malignant: A rare inherited disease that causes a rapid rise in body temperature and muscle rigidity when a person undergoes general anesthesia. Succinyl choline and halothane are the two drugs most associated with the condition. The result can be destruction of muscle tissue, kidney failure, and death may occur. The propensity to malignant hyperthermia is inherited in an autosomal dominant manner. One form of malignant hyperthermia is produced by mutation of the ryanodine receptor gene (RYR1). Treatment involves administration of dantrolene sodium (brand name: Dantrium) and rapid cooling of the patient.