Abstract
N-acetyl glutamate synthase (NAGS) deficiency is the rarest urea cycle defect presenting as neonatal onset life-threatening hyperammonemia. We report here a family history of severe NAGS deficiency: after the index-case with severe hyperammonemia, one patient benefited from antenatal diagnosis, and from primary care at birth, another one was diagnosed at 2-days and immediately treated with carbaglumic-acid. Finally, we report excellent tolerance to long-term carbaglumic-acid treatment, with no side effects, and healthy neurological and psychomotor development.
Highlights
N-acetyl glutamate synthase (NAGS) deficiency is an autosomal recessive disease that usually presents as neonatal onset life-threatening hyperammonemia
Severe NAGS deficiencies entailing the complete lack of the enzyme lead to severe neonatal hyperammonemia; late-onset presentations related to a partial lack of the enzyme have been reported in infancy, childhood, and adulthood [7]
Despite major hyperammonemia, the index case presented a favorable long-term outcome, mainly as a result of early care and treatment with N-carbamoyl glutamate. Her sister had the benefit of a prenatal diagnosis enabling management at birth to avoid hyperammonemia, without any neurological damage
Summary
N-acetyl glutamate synthase (NAGS) deficiency is an autosomal recessive disease that usually presents as neonatal onset life-threatening hyperammonemia. NAGS catalyzes the formation of N-acetyl glutamate by the combination of glutamate and N-acetyl CoA This molecule activates, in an allosteric manner, carbamoylphosphate synthetase I (CPSI), which is the first and rate-limiting enzyme of the urea cycle. Severe NAGS deficiencies entailing the complete lack of the enzyme lead to severe neonatal hyperammonemia; late-onset presentations related to a partial lack of the enzyme have been reported in infancy, childhood, and adulthood [7]. NAGS deficiency is the only urea cycle disorder that is curable This disease is currently treatable using carbaglumic acid (Carbaglu®), an analog of N-acetyl glutamate, and a low protein diet when initiating the treatment [5]. This report illustrates the overall picture of the disease, its management, and the value of early prenatal or pre-symptomatic diagnosis
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