Exercise-induced muscle "burning," fatigue, and hyper-CKemia: mtDNA T10010C mutation in tRNA(Gly).

A 42-year-old woman presented with myopathy and without a family history of neuromuscular disorder. Muscle biopsy showed ragged red fibers and reduced activities of mitochondrial respiratory chain enzyme complexes I, III, and IV. Analysis of mitochondrial DNA revealed a heteroplasmic T10010C mutation in the transfer RNA glycine gene.