N-Carbamylglutamate Is an Effective Treatment for Acute Neonatal Hyperammonaemia in a Patient with Methylmalonic Aciduria.

N-carbamylglutamate (NCG) has been used in combination with ammonia scavengers (sodium benzoate, sodium phenylbutyrate) and dialysis to treat hyperammonaemia in methylmalonic aciduria (MMA). The sole use of NCG for acute neonatal hyperammonaemia secondary to MMA is demonstrated in a neonate presenting at day 9 with encephalopathy, severe metabolic acidosis, hyperammonaemia (1,089 μmol/l), ketonuria and urinary methylmalonic acids. Emergency treatment included discontinuing protein feeds, providing high calories, carnitine and hydroxocobalamin. NCG 200 mg given at 0 and 90 min decreased plasma ammonia dramatically from 1,089 to 567 µmol/l at 90 min and further to 236 µmol/l at 6 h. Normalisation of ammonia was achieved at 12 h with two further doses of NCG 100 mg. This allowed for early re-institution of feeds at 14 h, followed by metabolic stabilization and recovery. Due to the effectiveness of NCG in this case, the use of the more invasive conventional ammonia-lowering therapeutic options could be avoided.