Hyperammonaemia in Neonates and Young Children: Potential Metabolic Causes, Diagnostic Approaches and Clinical Consequences

Hyperammonaemia is a metabolic disturbance characterized by accumulation of ammonia in the blood. Entry of ammonia into the brain via the blood-brain barrier leads to hyperammonaemic encephalopathy. The causes of hyperammonaemia in paediatric patients vary. We present 3 cases of hyperammonaemia in critically ill children in whom an inborn metabolic disorder was identified and provide insights into the phenotypes, diagnostic approaches and management. In children with acute overwhelming illness and progressive neurological deterioration plasma ammonia measurement should be included in the urgent diagnostic work-up. We here raise the awareness that hyperammonaemia is a metabolic emergency requiring prompt recognition and treatment to avoid subsequent complications.