We report on a now 13-year-old girl, who presented with recurrent episodes of vomiting, psychotic behaviour and confusion during puberty until the diagnosis of partial N-acetylglutamate synthetase deficiency was established. She had suffered one prior unclear episode of acute vomiting, lethargy and somnolence at the age of 13 months, and from childhood onward had aversion to high protein food. Treatment with a protein-restricted diet and administration of phenylbutyrate as well as L-arginine were sufficient to normalize ammonia levels but glutamine concentrations remained high. Supplementation with N-carbamylglutamate rapidly improved her protein tolerance and reduced the need for co-medication. To our knowledge, so far only seven patients with N-acetylglutamate synthetase deficiency have been reported.
Conclusion: Partial N-carbamylglutamate deficiency has to be considered in the differential diagnosis of hyperammonaemia. If proven by enzyme determination in liver tissue, the disorder should be cautiously treated with N-carbamylglutamate.