Glycine encephalopathy (GCE) is an inherited disorder caused by the build-up of glycine, a building block of proteins, in tissues and organs of the body, especially the brain. This is caused by a defective complex of enzymes that work together to break down glycine. GCE is also known as nonketotic hyperglycinemia. Typically symptoms begin to appear within the first few days of life. These symptoms include feeding difficulties, weak muscle tone, progressive lack of energy, and abnormal jerking movements and breathing problems. Death often occurs soon after in the most severe cases. For those children affected with GCE who survive infancy, they often develop intellectual disability and seizures as they get older, in addition to the previous symptoms. In some rare cases children may have milder symptoms that start to appear later on in infancy, or symptoms may not appear until adulthood. There is no cure for GCE, but medical care and surveillance may help to improve some symptoms and overall condition of life. One of the causes of GCE is pathogenic mutations in the GLDC gene.