Background: Ornithine transcarbamylase deficiency (OTC-D) is a urea cycle disorder caused by dysfunction of ornithine transcarbamylase, which frequently leads to hyperammonemia. Hyperammonemia represents a medical emergency requiring prompt treatment to reduce plasma ammonia levels and prevent severe neurological damage, coma, and death, particularly in patients with acute decompensation-related coma. The clinical symptoms of OTC-D can manifest themselves either at an early stage, which is often associated with severe symptoms, or in later life (late-onset OTC-D), when symptoms may be less severe. There is currently little agreement over diagnostic signs of the condition or the most appropriate therapeutic approach. Hyperammonemia is usually treated with ammonia scavengers, continuous venovenous hemodialysis, and dietary changes. N-carbamylglutamate is approved for the treatment of hyperammonemia in N-acetylglutamate synthetase deficiency and may have efficacy in other urea cycle disorders.
Methods/results: Here, we report a 13-year-old girl who was diagnosed with OTC-D at the age of 3 years. On this occasion, the patient presented with vomiting, lethargy, and mental confusion. Despite biochemical parameters being within normal ranges, she was comatose within a few hours. She was promptly treated with a combined therapy of continuous venovenous hemodialysis and N-carbamylglutamate, resulting in a gradual normalization of clinical symptoms within 30 hours. No neurological damage was apparent at 18 months after treatment.
Conclusions: This case demonstrates that clinical benefits can be obtained by beginning aggressive treatment of OTC-D within a few hours of the onset of severe neurological symptoms even in the absence of altered biochemical markers.