COQ4 and mitochondrial DNA depletion syndrome, encephalomyopathic form with methylmalonic aciduria: The initial evidence of COQ4 dysfunction as cause of encephalomyopathy was the report of Salviati et al.[32], who, in 2012, reported a 3.9-Mb deletion of chromosome 9q34.13 encompassing COQ4 in a 3-year-old boy with mental retardation, encephalomyopathy, and dysmorphic features who responded to CoQ10 supplementation (30 mg/kg per day of ubiquinone).