Glutaric aciduria type I (GA-I) is an autosomal recessive disorder caused by a deficiency of glutaryl-CoA dehydrogenase (GCDH; EC 1.3.99.7), a mitochondrial enzyme that catalyzes the oxidative decarboxylation of glutaryl-CoA to crotonyl-CoA in the catabolic pathway of lysine, hydroxylysine, and tryptophan [1–3]. The gene discussed is GCDH; the disease is glutaryl-CoA dehydrogenase deficiency.