Nonketotic hyperglycinemia in a newborn infant

A neonate with nonketotic hyperglycinemia who experienced apnea, hiccups and tonic-clonic seizures on the first day of life is reported. The physical findings and laboratory tests including arterial blood gases were normal. However, serial blood and CSF amino-acid analyses demonstrated elevated glycine levels. Serum and CSF glycine levels were 1949 mumol/L and 415.5 mumol/L, respectively. (Normal serum level is 104-254 mumol/L and CSF level is 5 +/- 2 mumol/L). The CSF/plasma glycine ratio was 0.11. Oral sodium benzoate and folic acid therapy was initiated. After two weeks of assisted ventilation and clinical improvement, the patient was discharged with a protein-restricted diet.