Propionic acidemia

Propionic acidemia, also known as propionic aciduria or propionyl-CoA carboxylase deficiency, is a rare autosomal recessive metabolic disorder and one of the branched-chain organic acidemias. Mutations in both copies of the PCCA or PCCB gene leave the enzyme propionyl-CoA carboxylase nonfunctional, so the amino acids valine, isoleucine, threonine and methionine, and some odd-chain fatty acids, cannot be fully broken down and propionic acid and other toxic compounds build up in the blood. Babies typically become ill in the first days of life with poor feeding, vomiting, lethargy and low muscle tone, and without treatment the condition can quickly prove fatal through high ammonia, infection, heart muscle disease or brain damage. Long-term effects can include intellectual disability, kidney disease and cardiomyopathy. Management centres on a low-protein diet, carnitine and careful handling of infections, and liver transplantation is gaining a role. It affects about one in 35,000 births in the United States and is more common in Saudi Arabia.