NAGS (N-acetylglutamate synthase) is a mitochondrial enzyme that catalyzes the synthesis of N-acetylglutamate (NAG), an essential allosteric activator of carbamoylphosphate synthetase I (CPS1) 1. By producing NAG, NAGS plays a critical role in regulating ureagenesis and ammonia detoxification through the urea cycle 1. The NAGS protein contains mitochondrial-targeting and acyl-CoA N-acyltransferase domains 1. NAGS deficiency is an autosomal recessive disorder causing hyperammonemia due to loss of CPS1 activation 1. Disease manifestations range from acute neonatal hyperammonemia to late-onset presentations 2. Molecular testing of NAGS mutations enables early diagnosis and carrier testing 12. Twenty-one disease-causing mutations have been identified distributed throughout the NAGS reading frame, with no mutations in exon 1 encoding the mitochondrial-targeting signal 2. NAGS deficiency is highly treatable with N-carbamylglutamate (NCG/Carbaglu), a NAG structural analog that activates CPS1 12. Early treatment initiation is critical to prevent severe neurological damage 2. NAGS was endorsed by 85% of rare disease experts for inclusion in newborn genome sequencing programs 3, reflecting its importance as a treatable condition.