Human mitochondrial respiratory chain deficiencies.

In this paper selected data from 43 patients with histologically defined mitochondrial myopathies who have been investigated biochemically as previously described are presented. The defect was localized to NADH-ubiquinone oxidoreductase (complex I) in 22 cases and to ubiquinol-cytochrome c oxidoreductase (complex III) in a further 10. Two patients had defects of more than one respiratory enzyme complex and another had a deficiency of H+-ATPase. The lesion was not localized in two cases and in vitro mitochondrial studies were normal in five cases.