Glutaric acidemia type II (GA-II), also known as Multiple Acyl-Coenzyme A Dehydrogenase Deficiency (MADD), is an autosomal recessive genetic disorder of fatty acid, some amino acid and choline oxidation, caused predominately by mutations in the α/β-subunit of Electron Transfer Flavoprotein (ETF, encoded by ETFA, ETFB) or Electron Transfer Flavoprotein-Ubiquinone Oxidoreductase (ETF-QO, encoded by ETFDH) (31–33) (Figure 3). Here, ETFDH is linked to multiple acyl-CoA dehydrogenase deficiency.