Clinical Practice and Cases in Emergency Medicine

Introduction: Citrullinemia type 1 (CTLN1) is a urea cycle disorder caused by defective argininosuccinate synthetase leading to impaired ammonia elimination. Urea cycle disorders are typically diagnosed on neonatal screening but rarely can lie dormant until a metabolic stressor causes initial onset of symptoms in adulthood.

Case Report: A 23-year-old female presented four days postpartum to the emergency department (ED) obtunded and declined to the point of requiring intubation. Labs revealed hyperammonemia, and she was subsequently found to have CTLN1.

Conclusion: Urea cycle disorders presenting in adulthood are a rare etiology for the common ED complaint of altered mental status. The low incidence makes these treatable disorders easy to overlook leading to potentially significant morbidity and mortality. Therefore, it is important to recognize the risk factors that can trigger an acute metabolic derangement. This case highlights common risk factors for metabolic stress, possible presenting symptoms, and the positive outcome achievable when recognized and treated in a timely fashion.