GCDH and glutaryl-CoA dehydrogenase deficiency: The mitochondrial catabolism of lysine and tryptophan is disrupted by a deficiency of glutaryl-coenzyme A dehydrogenase (EC 1.3.99.7) (GCDH), causing glutaric aciduria type 1 (GA1) (OMIM #231670), which leads to the accumulation of glutaryl-CoA, glutaric acid (GA), 3-hydroxyglutaric acid (3-OHGA) and glutaconic acid (GC) in body fluids and tissues [1]–[4].