Glutaconic acid is related to the fully saturated glutaric acid and belongs to the class of compounds known as dicarboxylic acids and derivatives. These are organic compounds containing exactly two carboxylic acid groups. Glutaconic acid is soluble (in water) and a weakly acidic compound (based on its pKa). Glutaconic acid has been detected in the urine of individuals with inborn errors of metabolism. When present in sufficiently high levels, glutaconic acid can act as an acidogen, a neurotoxin, and a metabotoxin. An acidogen is an acidic compound that induces acidosis, which has multiple adverse effects on many organ systems. A neurotoxin is a compound that is toxic to neural tissues and cells. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. Chronically high levels of glutaconic acid are associated with glutaric aciduria type I (glutaric acidemia type I, glutaryl-CoA dehydrogenase deficiency, GA1, or GAT1). GA1 is an inherited disorder in which the body is unable to completely break down the amino acids lysine, hydroxylysine and tryptophan. Excessive levels of their intermediate breakdown products (e.g. glutaric acid, glutaryl-CoA, 3-hydroxyglutaric acid, glutaconic acid) can accumulate and cause damage to the brain (and also other organs). Babies with glutaric acidemia type I are often born with unusually large heads (macrocephaly). Macrocephaly is amongst the earliest signs of GA1. GA1 also causes secondary carnitine deficiency because glutaconic acid, like other organic acids, is detoxified by carnitine. Abnormally high levels of organic acids in the blood (organic acidemia), urine (organic aciduria), the brain, and other tissues lead to general metabolic acidosis. Acidosis typically occurs when arterial pH falls below 7.35. In infants with acidosis, the initial symptoms include poor feeding, vomiting, loss of appetite, weak muscle tone (hypotonia), and lack of energy (lethargy). These can progress to heart, liver, and kidney abnormalities, seizures, coma, and possibly death. These are also the characteristic symptoms of untreated glutaric aciduria. Many affected children with organic acidemias experience intellectual disability or delayed development. In adults, acidosis or acidemia is characterized by headaches, confusion, feeling tired, tremors, sleepiness, and seizures. Glutaconic acid's neurotoxicity is thought to be partially caused by an excitotoxic mechanism in which glutaconic acid overactivates N-methyl-D-aspartate (NMDA) receptors. Accumulating trans-glutaconic (TG) acids have been proposed to be involved in the development of the striatal degeneration seen in children with glutaric acidemia type I via an excitotoxic mechanism.