Positive Malignant Hyperthermia Susceptibility In Vitro Test in a Patient with Mitochondrial Myopathy and Myoadenylate Deaminase Deficiency

MALIGNANT hyperthermia (MH) is a life-threatening anesthesia-related complication characterized by a hypermetabolic response of skeletal muscle which can be triggered by anesthetic drugs such as halothane and succinlcholine. 1 Although some genes have been identified to be involved in MH (such as the ryanodine receptor gene [RYR1] and the dihydropyridine receptor [DHP] gene) the underlying molecular defect remains unclear in the majority of MH-cases. However, apart from central core disease, which is regularly associated with MH-susceptibility, the association of other neuromuscular diseases with MH has been reported anecdotally. Here we report a 41-yr-old man with a long history of progressive muscle weakness, myalgia, and recurrent myoglobinuria due to two unrelated metabolic defects, i.e., mitochondrial myopathy in combination with myoadenylate deaminase (MAD) deficiency. The patient tested positive for malignant hyperthermia susceptibility (MHS) by the halothane caffeine in vitro contracture testing (IVCT) procedure.