D-glycericacidemia
Overview
Glycine encephalopathy, also known as non-ketotic hyperglycinemia or NKH, is an autosomal recessive metabolic disorder characterized by abnormally high levels of the amino acid glycine. Glycine acts as a neurotransmitter, which is a chemical messenger that transmits signals in the brain.
Symptoms
Most patients with GCE have the neonatal phenotype, presenting in the first few days of life with lethargy, hypotonia, and myoclonic jerks,and progressing to apnea, and often to death. Those who regain spontaneous respiration develop intractable seizures and profound mental retardation.
Causes
Mutations in the AMT and GLDC genes cause glycine encephalopathy. About 80 percent of cases of glycine encephalopathy result from mutations in the GLDC gene, while AMT mutations cause 10 percent to 15 percent of all cases. In a small percentage of affected individuals, the cause of this condition is unknown.