[MIM*238300] an inborn error of glycine metabolism, due to a deficiency of glycine dicarboxylase P protein (GCSP), a component of glycine cleavage system; characteristically overwhelming disease in the newborn period, with coma, seizures, and death, or, less often, gradual onset with failure to thrive, focal seizures, and mental retardation; there is massive elevation of plasma glycine, with increased levels in cerebrospinal fluid and urine; plasma hyperosmolality, severe dehydration occur without ketoacidosis; autosomal recessive inheritance; caused by mutation in the GCSP gene on chromosome 9p.