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An abnormal exercise test response revealing a respiratory chain complex III deficiency
B Mousson1, J M Collombet, R Dumoulin
1Laboratoire de Biochimie Pédiatrique, Hôpital Debrousse, Lyon, France.
Acta Neurologica Scandinavica
|June 1, 1995
Summary
This study identifies a mitochondrial myopathy in a patient with exercise intolerance. A deficiency in complex III activity was found, explaining the muscle
Area of Science:
- Biochemistry
- Exercise Physiology
- Neuromuscular Disorders
Background:
- Mitochondrial myopathies are a group of inherited disorders affecting muscle energy production.
- Exercise intolerance is a common symptom, often linked to impaired aerobic metabolism.
Observation:
- A 29-year-old male presented with progressive exertional muscle intolerance since childhood.
- Incremental exercise testing revealed reduced maximal oxygen consumption and an early anaerobic threshold.
- Metabolic investigations showed hyperlactataemia and an elevated lactate/pyruvate ratio at rest and post-meal.
Findings:
- Muscle biopsy revealed characteristic red granular deposits in type 1 fibers.
- Biochemical analysis demonstrated a significant deficiency in ubiquinol cytochrome c reductase (Complex III) activity within the mitochondrial respiratory chain.
Implications:
- This case highlights Complex III deficiency as a cause of mitochondrial myopathy presenting with exercise intolerance.
- Understanding specific enzyme defects is crucial for accurate diagnosis and potential therapeutic strategies in mitochondrial diseases.