FAILURE OF EARLY DEXTROMETHORPHAN AND SODIUM BENZOATE THERAPY IN AN INFANT WITH NONKETOTIC HYPERGLYCINEMIA

We report an infant with neonatal nonketotic hyperglycinemia (NKH), di agnosed early and treated with dextromethorphan (DM) and sodium benzoa te therapy from the 65th hour of life. Initially the patient responded to treatment showing clinical and electroencephalographic improvement : myoclonic jerks disappeared, muscular tone, reactivity to stimuli an d spontaneous movements increased, assisted ventilation was no longer necessary and bottle feeding was initiated successfully; on EEG the su ppression-burst pattern disappeared and the background activity was we ll-organized. At three months of age he developed flexor spasms and hy psarrhythmia. In spite of increasing doses of DM as high as 40 mg/kg/d ay and persistent therapy with sodium benzoate the child progressively deteriorated and died at the age of 5 months and 7 days. We stress th at the adverse clinical course occurred in our patient even though DM and sodium benzoate therapy was started much earlier than in other rep orted cases. It is possible that prenatal brain damage and probable ge netic variants (i.e. absent or minimal residual enzymatic activity and interindividual variations in DM metabolism) affect the response to t herapy.