Pediat. Extract showed constantly elevated levels of glycine (6.0-10.0Our previous study demonstrated a block in glycine cleavage reaction in the liver from two patients with hyperglycinernia of the nonketotic type. The present study extended this work t o two other patients with nonketotic hyperglycinernia and a patient with ketotic hyperglycinemia. The liver specimens obtained from these patients by autopsy or biopsy were studied for the activities of glycine cleavage reaction and of serine hydroxymethylase.A low activity of glycine cleavage reaction was found in all three patients with nonketotic or ketotic hyperglycinemia, whereas the activity of serine hydroxymethylase remained within normal limits. Speculation mg/100 ml) and normal levels of propionic acid, methylmalonic acid, and isovaleric acid in the blood. No ketoacidosis was present. The liver specimen was biopsied at the age of 5 years.Case LK, a girl (nonketotic hyperglycinemia), was born after a full term pregnancy and spontaneous delivery. The girl was normal up t o the 4th day of life, when she was found t o be comatose and hypotonic. Laboratory examinations revealed a high level of serum glycine (17 mg/100 ml) and normal levels of propionic acid, methylmalonic acid, and isovaleric acid in blood.No ketoacidosis was present. The patient died on the 5 t h day of life and the Liver specimen was obtained immediately after death.Case VA, a girl (ketotic hyperglycinemia), was born after a full term pregnancy and spontaneous delivery. She began t o The present suggests that a in the glycine vomit in the lst week of life. The was hospitalized at the cleavage reaction, either primarily or secondarily, plays a n important role in glycine accumulation in both types of age of 2.5 months, when she was comatose, dehydrated, and hyperglycinemias.grossly underweight. Laboratory examinations showed a high level of serum glycine (9.0 mg1100 ml) and a remarkable elevation of propionic acid (716 rng/lOO ml) and methylHyperglycinemia represents a group of disorders charac-malonic acid (12.1 mg/100 ml). Marked acidosis was present, terized by elevated concentrations of glycine in body fluids. indicating blood Ph 7.06, H e 0 3 9.5 mEq/liter, and acetonuria. The disorder is now divided into two forms, the ketotic and She died 4 8 hr after admission in spite of intravenous fluid the nonketotic. In nonketotic hyperglycinemia, a defect of the therapy and peritoneal dialysis. The liver specimen was glycine cleavage enzyme in the liver was found t o be obtainedimmediatel~ after death. responsible for the accumulation of glycin (5,12,13). On the Case OR ( t r i s o m~ 13) died a t 4 months of postnatal age; other hand, it has been demonstrated that ketotic hyper-the liver specimen was obtained immediately after death. glycinemia is virtually due t o propionic acidemia, methylCase MM (congenital heart disease) died at 3 days of malonic acidemia, isovaleric acidemia (2, 6, 11). However, the postnatal age; the liver specimen was obtained immediately mechanisms of abnormal accu...