Nonketotic hyperglycinemia (NKH) is a rare disorder of glycine degradation with autosomal recessive inheritance.1 There are about 120 cases reported in the literature,2 and most of them represent a neonatal type of NKH. The defect in the glycine cleavage reaction, which has been demonstrated in both liver3 and brain4 tissue of the patients, leads to an accumulation of glycine. This is accompanied by the rapid development of severe neurologic symptoms.
If not lethal in the neonatal period, NKH leads to severe psychomotor retardation. The pathogenesis of the neurologic symptoms is not well understood, but the failure of the therapeutic experiments5,6 and the observation of a delay in the process of myelination in neonates dying of NKH7 suggest that an abnormal metabolism of glycine also exists in the fetus with NKH.
To study this particular aspect, we performed consecutive recordings of EEGs and determinations of