Nonketotic hyperglycinemia presenting with pin-point pupils and hyperammonemia

We describe two siblings who presented with lethargy, decreased sucking, respiratory failure and seizures in their first days of life. Pin-point pupils were noted in both siblings. Amino acid analysis revealed elevated concentrations of glycine in plasma and cerebrospinal fluid (CSF), with abnormal CSF/plasma ratios, compatible with hyperglycinemia. Urine organic acid analysis was unremarkable. Hyperammonemia was found in both siblings, but this subsided within 24-72 h. We suggest that pin-point pupils may be an additional presenting sign of nonketotic hyperglycinemia and, if looked for early enough, hyperammonemia may be found in this disorder.