Agenesis of the corpus callosum and gyral malformations are frequent manifestations of nonketotic hyperglycinemia.

A 2-week-old infant who presented with myoclonic encephalopathy had biochemical abnormalities consistent with nonketotic hyperglycinemia. Cranial CT showed agenesis of the corpus callosum, gyral malformation, and ventricular enlargement. Similar brain abnormalities occurred in 9 of 15 previously reported patients. Including this patient, agenesis of the corpus callosum appeared in 6 of 15 patients, gyral malformation in 6 of 14, ventricular enlargement in 5 of 15, and cerebellar hypoplasia in 2 of 16. Nonketotic hyperglycinemia thus joins a growing list of inborn errors of metabolism associated with brain malformations.