Urea Cycle Disorders & Hyperammonemia | USMLE Step 1
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A 17-year-old girl is brought to the emergency department for vomiting and confusion during a viral illness. She has eaten very little for two days. Her family recalls that she has avoided meat since childhood and that a maternal uncle died during the first week of life. Plasma ammonia is 286 µmol/L, plasma citrulline is 5 µmol/L (reference, 12–44), and urinary orotic acid is markedly increased. Urgent treatment is started.