[Adult onset mitochondrial myopathy without ophthalmoplegia. Four cases attributable to complex III and IV deficits in the respiratory chain].

Four adults with proximal myopathy of mitochondrial origin but no ocular involvement are presented. Biochemical analysis showed combined complex III and IV deficits in the respiratory chain in all cases, suggesting an apparent correlation between clinical phenotype and biochemical findings. Mitochondrial DNA analysis of muscle from 1 patient failed to detect either large-scale deletion or point mutations at position 3243 of tRNA(Leu(UUR)) or at 8344 of tRNA(Lys). The tissue specificity of the disease and the absence of family history suggest that a mutation in a nuclear DNA gene encoding a specific subunit of muscle could underlie this disease.