Mitochondrial DNA point mutation in the COI gene in a patient with McArdle's disease.

We studied a 57-year-old female patient with clinical and biochemical evidences of McArdle's disease. Her muscle biopsy also revealed signs of mitochondrial proliferation, scattered RRF, and a deficit in complex I of the respiratory chain. Molecular genetic analysis showed that the patient was heterozygous for the most common mutation at codon 49 in the myophosphorylase gene. Mitochondrial DNA analysis of muscle tissue revealed an additional G-to-A transition at nucleotide position 7444 in the cytochrome c oxidase subunit I (COI) gene.