An abnormal exercise test response revealing a respiratory chain complex III deficiency |
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Authors: | B Mousson J M Collombet R Dumoulin H Carrier F Flocard M Bouzidi C Godinot I Maire M Mathieu S Quard |
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Institution: | Laboratoire de Biochimie Pediatrique, v Debrousse;Département de Recherche Neuromusculaire (CNRS EP 18);Service de Neurologie, HIA Desgenettes;Hôpital Cardiologique - Medica Sport, Lyon;UMR 106 - CNRS - UCB Lyon I, Villeurbanne, France |
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Abstract: | A 29-year-old man with a progressive exertional muscle intolerance since childhood was referred for incremental exercise test on a bicycle ergometer. The response pattern suggested a mitochondrial myopathy: that is, a greatly reduced maximum oxygen consumption with appropriate heart rate increase and an anaerobic threshold point reached early. The metabolic investigation in plasma revealed an abnormal oxidoreduction status (hyperlactataemia and high lactate/pyruvate ratio) at rest and after a carbohydrate rich meal. The histochemical examination of a muscle biopsy revealed red granular deposits under the sarcolemma for all type 1 fibers. Oxypolarographic and enzymological studies of the mitochondrial respiratory chain in both isolated mitochondria and muscle homogenate demonstrated a marked deficiency of ubiquinol cytochrome c reductase (complex III) activity. |
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Keywords: | exercise test exercise intolerance mitochondrial myopathy respiratory chain complex III |
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