ETFDH and multiple acyl-CoA dehydrogenase deficiency: Secondary CoQ10 defect has already been reported in patients with mitochondrial diseases or dysfunctions including Kearns–Sayre syndrome [24], mtDNA depletion and PEO [5] or mutations in ETFDH coding for electrontransferring-flavoprotein dehydrogenase and causing MADD [8, 9].