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.