A Case of Severe Neonatal Hyperammonemia

A male child was delivered by caesarian section for nonreassuring fetal heart tracings at 39 weeks of gestation. He emerged limp and cyanotic without respiratory effort. He was intubated, suctioned for thick meconium, and given positive pressure ventilation, during which he developed spontaneous respiration. He was further treated with boluses of saline and glucose for hypotension and hypoglycemia, respectively. He also had thrombocytopenia. He was treated with empiric antibiotics until blood cultures were reported negative. After initially showing some feeding intolerance, he reached full enteral feeding by day 4. However, by day 5, he had less coordinated feeding and developed apnea and seizures for which treatment included intubation, mechanical ventilation, phenobarbital administration, and empiric antibiotics reinstitution. Around this time, newborn screen results became available and were concerning for low–normal citrulline levels. A metabolic disorder was considered. Plasma ammonia concentration measurement showed marked hyperammonemia (plasma ammonia = 2090 μmol/L; reference interval = <90) with increases in plasma glutamine (1536 μmol/L; reference interval: 330–1080) and alanine (1160 μmol/L; reference interval: 120–500) concentrations. Plasma citrulline concentration was 3 μmol/L (reference interval: 2–50). Family history was unremarkable with no previous neonatal deaths. A urine specimen was collected …