Propionic acidemia also known as propionic aciduria or ketotic glycinemia is an uncommon metabolic disorder which is characterized by the deficiency of propionyl CoA carboxylase (an enzyme that is involved in breaking down the amino acids). It is categorized as branched-chain organic acidemia which often presents symptoms early on in the neonatal period which comes with progressive encephalopathy.

Propionic acidemia is an autosomal recessive disease which can be inherited. This disorder is found in approximately 1 of 35,000 births in the US alone. This condition is a common illness in Saudi Arabia manifesting 1 in every 3,000 births. The Amish and Mennonite populations have many cases of this illness.

Mutations of the PCCA or the PCCB genes (in both copies) cause the propionic acidemia. The two genes are the ones that are responsible in the formation of the propionyl-CoA carboxylase enzyme (EC 6.4.1.3), called as PCC. PCC is needed to make a normal breakdown of the important amino acids isoleucine, valine, methionine and threonine, also other fatty acids that are odd-chained. The mutations of PCCA or PCCB disrupt the enzyme functions, thus hampering metabolism of these acids. The result is an accumulation in the blood of compounds such as propionyl-CoA, ketones, propionic acid, and other lethal compounds. This accumulation triggers propionic acedemia.

Regimens of treatment for this disorder are complicated. The diet is protein-restricted and the administration of a formula that has been specially prepared is needed. L-carnitine may be of help to replenish the extracellular and intracellular storage of free carnitine. Oral administration of antibiotics could prove to be useful in decreasing propionate gut production, or the usage of a laxative in increasing motility of the gut. Continuous feedings throughout the night may help in the decrease of beta-oxidation and also the release of fatty acids that are odd-chained (theoretically, this is believed to inhibit lipolysis). Transplant of the liver helps protect against severe metabolic decompensation.

The symptoms occur and become apparent on the first few weeks of an infant's life and it may include unusually reduced muscle tone or hypotonia; listlessness or lethargy; poor feeding; extreme loss of fluid from body tissues (also termed as dehydration); and uncontrolled episodes of electrical activities in one's brain typically known as seizures. If treatment is not given immediately, this disorder could result into coma or it could be fatal for the patient. Death can happen very quickly because of secondary hyperammonemia, cardiomyopathy, infection or stroke of the basal ganglia. In very rare instances, the disorder may become obvious on the later part of infancy and it may be linked with less acute findings and symptoms. Propionic acedemia is an inherited autosomal recessive trait.

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