Early continuous blood purification and timely liver transplantation in a neonatal-onset ornithine transcarbamylase deficiency: a case report.

Background: Ornithine transcarbamylase deficiency (OTCD) is the most common urea cycle disorder (UCD), caused by a deficiency of the OTC enzyme, leading to the accumulation of toxic ammonia in the blood. Neonatal-onset OTCD is associated with high mortality and severe neurodevelopmental impairments. Symptoms are often non-specific and can mimic neonatal sepsis. If untreated, the condition can rapidly progress to neurological damage. Early diagnosis and prompt intervention are crucial for improving survival and long-term outcomes. Case Description: We report a case of a 9-day-old male infant diagnosed with neonatal-onset OTCD, who presented with lethargy and poor feeding. Initial ammonia levels were found to be elevated at 428 µmol/L, prompting the initiation of supportive care, including protein restriction and intravenous arginine. However, the patient's ammonia level rose sharply to 1,150 µmol/L within 20 hours, prompting the initiation of continuous veno-venous hemodiafiltration (CVVHDF). Following CVVHDF, ammonia levels decreased to 145 µmol/L within 24 hours. Genetic testing confirmed a hemizygous pathogenic variant (c.542A>G) in the OTC gene, confirming the diagnosis of OTCD. After clinical stabilization, he was discharged on a low-protein diet with supplementation. At 8 months, the patient underwent successful orthotopic liver transplantation using a graft from a donor after circulatory death. Postoperatively, he made an uneventful recovery, with stable graft function. At 1 year of age, he exhibited favorable metabolic control and age-appropriate developmental progress. Conclusions: This case highlights the importance of early diagnosis and intervention in neonatal-onset OTCD. Timely application of continuous blood purification (CBP) followed by liver transplantation resulted in significant improvements in both metabolic control and neurodevelopment.