Coenzyme Q₁₀ is frequently reduced in muscle of patients with mitochondrial myopathy

Coenzyme Q₁₀ (CoQ₁₀) deficiency has been associated with an increasing number of clinical phenotypes. Whereas primary CoQ₁₀ defects are related to mutations in ubiquinone biosynthetic genes, which are now being unraveled, and respond well to CoQ₁₀ supplementation, the etiologies, and clinical phenotypes related to secondary deficiencies are largely unknown. The purpose of this multicenter study was to evaluate the frequency of muscle CoQ₁₀ deficiency in a cohort of 76 patients presenting with clinically heterogeneous mitochondrial phenotypes which included myopathy among their clinical features. A reliable diagnostic tool based on HPLC quantification was employed to measure muscle CoQ₁₀ levels. A significant proportion of these patients (28 over 76) displayed CoQ₁₀ deficiency that was clearly secondary in nine patients, who harbored a pathogenic mutation of mitochondrial DNA. This study provides a rationale for future therapeutic trials on the effect of CoQ₁₀ supplementation in patients with mitochondrial diseases presenting with myopathy among clinical features.