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Case Reports
. 1999 Jun;45(6):820-3.
doi: 10.1002/1531-8249(199906)45:6<820::aid-ana22>3.0.co;2-w.

Exercise intolerance due to a nonsense mutation in the mtDNA ND4 gene

A L Andreu  1 , K Tanji, C Bruno, G M Hadjigeorgiou, C M Sue, C Jay, T Ohnishi, S Shanske, E Bonilla, S DiMauro
Affiliations
Case Reports

Exercise intolerance due to a nonsense mutation in the mtDNA ND4 gene

A L Andreu et al. Ann Neurol. 1999 Jun.

Abstract

We report the first molecular defect in an NADH-dehydrogenase gene presenting as isolated myopathy. The proband had lifelong exercise intolerance but no weakness. A muscle biopsy showed cytochrome c oxidase (COX)-positive ragged-red fibers (RRFs), and analysis of the mitochondrial enzymes revealed complex I deficiency. Sequence analysis of the mitochondrial genes encoding the seven NADH-dehydrogenase subunits showed a G-to-A transition at nucleotide 11832 in the subunit 4 (ND4) gene, which changed an encoded tryptophan to a stop codon. The mutation was heteroplasmic (54%) in muscle DNA. Defects in mitochondrially encoded complex I subunits should be added to the differential diagnosis of mitochondrial myopathies.

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