tGA, or (E)-pentene-1,5-dioic acid, is an unsaturated C5-dicarboxylic acid that is found in patients affected by glutaric aciduria type I. Its role on this organic aciduria pathogenesis is under debate, since there are patients affected by glutaric aciduria type I who do not present tGA accumulation [3]. The gene discussed is TBX1; the disease is glutaryl-CoA dehydrogenase deficiency.