Mutations in ETFα and ETFβ and in the ETF-ubiquinone oxidoreductase are associated with the human inherited metabolic disease, glutaric acidemia type II or multiple acyl-CoA dehydrogenase deficiency (63, 64), and deletion of Lys-201 in mature ETFβ has been observed in a patient suffering from ETF deficiency (65). Here, ETFDH is linked to multiple acyl-CoA dehydrogenase deficiency.