Journal of Advanced Intensive and Critical Care Medicine

Abstract

Background: Metabolically defective classic infantile hyperammonemia is an infrequent but substantial diagnosis that can be obscured and lead to rapid development of cerebral edema with vasogenic brain injury when not identified early. In newborns, urea cycle disorders [1] are the most frequent cause of severe hyperammonemia. These disorders manifest at a similar stage of echocardiographic development as sepsis and very-early-onset infection (VUE) [2].

Case Presentation: A lethargic term male infant with poor feeding and tachypnea at 36 h of life was suspected to have early-onset neonatal sepsis. Despite being placed on antibiotics, the baby’s neurological status gradually declined. Tests revealed they had a very high level of serum ammonia (428 µmol/L) at a time when it should have been 15 to 45 µmol/L, and an MRI of the brain showed swelling in all dimensions, labeled “hyperammonemic encephalopathy.” She would immediately start metabolic management with protein restriction, intravenous glucose delivery, ammonia-scavenging therapy, and urgent hemodialysis. This resulted in an early biochemical remission, with the clinical status being stable. A urea cycle disorder was revealed by a later metabolic test.

Conclusion: This case highlights the diagnostic challenge of distinguishing metabolic disorders from neonatal sepsis. Early measurement of serum ammonia levels should be considered in neonates presenting with unexplained neurological deterioration or poor response to antibiotic therapy. Prompt recognition and treatment are essential to prevent severe neurological complications.