A case of late-onset carbamoyl phosphate synthetase 1 deficiency: diagnostic challenges and management in a low-resource setting.

OBJECTIVE

This study aimed to analyze the clinical features, genetic basis, and management of late-onset carbamoyl phosphate synthetase 1 deficiency (CPS1D) through a pediatric case report and literature review, highlighting diagnostic challenges and therapeutic strategies.

METHODS

We present a 19-year-old female with recurrent neurological symptoms since age 8. She underwent comprehensive metabolic screening, neuroimaging, and whole-exome sequencing of theCPS1gene. Identified variants were assessed for pathogenicity using multiple orthogonalin silicoprediction tools.

RESULTS

The patient's initial hyperammonemic crisis at age 8 was misdiagnosed as encephalitis. Workup at age 13 confirmed hyperammonemia (peak 168 µmol/L), hypocitrullinemia, and elevated glutamine. Genetic analysis identified compound heterozygousCPS1variants: a novel c.1058 T > C (p.F353S) and known pathogenic c.1145C > T (p.P382L). A self-selected low-protein diet controlled acute crises but led to severe growth failure (height 145 cm, weight 30 kg).

CONCLUSION

Late-onset CPS1D's nonspecific neurological symptoms often lead to misdiagnosis. Diagnosis requires a high index of suspicion, integrating metabolic profiling with genetic confirmation. This case expands the pathogenic genotypic spectrum of CPS1D. It crucially highlights that while dietary management is life-saving, it requires expert multidisciplinary oversight to prevent devastating consequences like growth failure, especially in resource-limited settings. Routine ammonia testing in unexplained encephalopathy is paramount.