Occasionally, patients with mitochondrial disorder (MID) develop malignant hyperthermia (MH)-like reactions or show an abnormal halothane-caffeine in-vitro contracture test. In a 66 year old Caucasian male with facial dysmorphism, epilepsy, chronic muscle cramps, repeatedly elevated creatine-kinase, Dupuytren contracture, and hypertrophic cardiomyopathy, a MID was found upon the clinical presentation, blood chemical investigations, and the muscle biopsy findings. Upon request of the anesthesiologists prior to surgery of a hernia cicatrices a halothane-caffeine in-vitro contracture test was carried out according to the protocol of the European MH Group (EMHG), showing abnormal hypercontractility to halothane and caffeine, resulting in the diagnosis susceptible MH according to the EMHG guidelines. Subsequent general anesthesia was carried out without complications by avoiding volatile anesthetics and succinylcholine. In the past the patient had already tolerated four procedures under general anesthesia, without any complication. MIDs may be associated with an abnormal halothane-caffeine in-vitro contracture test. Though previous general anesthesias had been carried out without major complications, it cannot be ruled out that MH-like manifestations may develop during future anesthesias if trigger agents are not avoided.