LAUSR

Background We report a clinical-biochemical findings in a child who presented with acute hyperammonemic encephalopathy. Methods Case notes and electronic record was used to collect data Results A 21 month old male child presented to accident and emergency with history of diarrhoea and vomiting for 2 days, but became progressively lethargic, unresponsive at home with grunty respirations. On arrival to A and E he was noted to be poorly perfused, with reduced consciousness. Needed 30 ml/kg fluid bolus through intra-osseous route. He had metabolic acidosis which was partially corrected with the fluid bolus. After a brief period of being stable on the ward he became suddenly unresponsive, tachyopneic needing intubation and mechanical ventilation and transfer to PICU. At PICU he had had further bloods including ammonia in view of acidosis, the ammonia was significantly elevated at 850 mmol/L along with elevated lactates. He was commenced on emergency regime of sodium benzoate, sodium phenyl butyrate along with arginine and carglumic acid. He also needed haemofiltration to manage hyperammonemia. His ammonia normalized over 18 hours. Plasma amino acid showed high levels of glutamine, tyrosine, lysine and aspartate with low citrulline. Urinary organic acids demonstrated increased lactic acid, large increase in 3 hydroxybutyrate and acetoacetate with appropriate increase in MCFA(medium chain fatty acids)-normal response to fasting or hypoglycemia. However DNA analysis did not confirm a diagnosis of OTC deficiency. He has been discussed with Great Ormond St team who opine that OTC deficiency is very likely, however as per their advice DNA has been sent for hyperammonemia extended metabolic panel. He has an emergency plan in place if becomes unwell and has an emergency kit containing essential drugs. Conclusion Urea cycle disorders should be considered in the differential diagnosis of patients who present with symptoms of acute hyperammonemia. If a urea cycle disorder is being considered, treatment should be started prior to confirmation of the diagnosis. Only by clinical suspicion and careful investigation will inborn errors of metabolism be uncovered and treated in a timely manner.