Nonketotic hyperglycinemia, abbreviated NKH, is a metabolic disorder in which too much glycine — a basic amino acid — is found in the blood, cerebrospinal fluid and urine, says the NKH-International Family Network. The high glycine levels occur because of a shortage of an enzyme that normally breaks down the glycine molecule, according to the Genetics Home Reference. The resulting buildup of glycine causes seizures, severe to profound mental retardation, lethargy, poor muscle tone and respiratory difficulties. The condition affects both boys and girls, but boys are more likely to survive and have less severe mental retardation.
The rare genetic condition, which has no cure or proven treatment, is also known as glycine encephalopathy. Studies in Finland and Canada suggest NKH affects approximately one child per 60,000 births, says the Genetics Home Reference. For more information, visit www.nkh-network.org.
