Malignant hyperthermia

Malignant hyperthermia (MH) is a rare autosomal dominant genetic disease of calcium (Ca2+) metabolism in skeletal muscle. Its manifestations are normally silent and only made evident when susceptible patients receive general anaesthesia with volatile anaesthetic agents or succinyldicholine. Skeletal muscle hypermetabolism triggered by exposure to these agents causes a cascade of clinical events, rapidly leading to death. Early treatment with dantrolene can abort the syndrome. Muscle from MH patients is abnormally sensitive to caffeine, and this forms the basis of the halothane/caffeine contracture diagnostic test. MH susceptibility has been linked to the skeletal muscle Ca2+release channel gene (ryanodine receptor, RYR1) on chromosome 19 and four other loci related to skeletal muscle excitation contraction coupling. Over 30 RyR1 mutations from three ‘hot spot’ regions have been found. Discordance between some mutations and MH susceptibility has prevented genetic testing from being generally useful for diagnosis. The effects of MH mutations on RyR1 channel physiology will be presented. The roles of other proteins including FKBP12, the slow voltage-gated channel, and calsequestrin on MH will be discussed.