Non-ketotic hyperglycinemia (NKH) is an ultra-rare (incidence 1/76,000 births) genetic, neurometabolic disorder caused by deficient enzyme activity of the glycine cleavage enzyme (GCE) (EC 1.4.4.2) due to mutations in GLDC encoding the P-protein or AMT encoding the T-protein. This evidence concerns the gene GLDC and glycine encephalopathy.