COQ9 and mitochondrial DNA depletion syndrome, encephalomyopathic form with methylmalonic aciduria: While the determination of pathogenic variants in COQ9 is rare, mutations in the COQ9 gene are associated with primary CoQ10 deficiency and are further associated with several disease states, predominantly encephalomyopathy and an autosomal-recessive neonatal-onset CoQ10 deficiency [29].