Rebound hyperammonemia triggered by interruption of renal replacement therapy in adolescent ornithine transcarbamylase deficiency

Ornithine transcarbamylase (OTC) deficiency is the most common urea cycle disorder (UCD) and may lead to life-threatening hyperammonemia. Refractory cases require prompt and aggressive treatment, including renal replacement therapy (RRT), to prevent irreversible neurological damage.

We encountered a 14-year-old girl with OTC deficiency who presented with severe hyperammonemia (649 µg/dL;382 µmol/L). Pharmacological therapy and emergency intermittent hemodialysis (IHD) were followed by continuous hemodiafiltration (CHDF), resulting in rapid ammonia clearance. However, a 4-h interruption of CHDF due to catheter replacement led to rebound hyperammonemia (>500 µg/dL;>294 µmol/L), requiring resumption of RRT on day 4. OTC deficiency was subsequently diagnosed based on plasma amino acid and urine organic acid analyses on day 12. After intensifying the pharmacological therapy and achieving stable ammonia levels, RRT was discontinued on day 17. The patient recovered without apparent neurological sequelae and was discharged from the intensive-care unit.

This case highlights the importance of uninterrupted RRT in managing acute hyperammonemia and suggests that even short pauses in CHDF can provoke clinically significant rebound. Early initiation of RRT, continuous monitoring of ammonia levels, and individualized treatment strategies are critical for optimizing patient outcomes. J. Med. Invest. 72 : 443-446, August, 2025.