A new mitochondrial myopathy. Biochemical studies revealing a deficiency in the cytochrome b-c1 complex (complex III) of the respiratory chain.
A 20-year-old Chilean girl presented with lifelong ptosis and fatiguable weakness which was initially thought to be due to a congenital myasthenic syndrome. Studies of an intercostal muscle biopsy showed normal endplate morphology, abundant acetylcholinesterase activity and a normal number of junctional acetylcholine receptors as determined by radiochemical assay, but a high proportion of the muscle fibres contained large peripheral aggregations of abnormal mitochondria. Biochemical investigation of mitochondria isolated from the vastus lateralis muscle demonstrated a hitherto unreported respiratory chain deficiency localized to complex III.
D000328:Adult; D003573:Cytochrome b Group / Q000378:metabolism; D003574:Cytochrome c Group / Q000378:metabolism; D005260:Female; D006801:Humans; D008854:Microscopy, Electron; D008931:Mitochondria, Muscle / Q000378:metabolism* / Q000648:ultrastructure; D009468:Neuromuscular Diseases / Q000378:metabolism* / Q000473:pathology; D009469:Neuromuscular Junction / Q000378:metabolism; D010085:Oxidative Phosphorylation; D013772:Tetramethylphenylenediamine / Q000378:metabolism
D003573:Cytochrome b Group; D003574:Cytochrome c Group; D013772:Tetramethylphenylenediamine