eMedicine Specialties > Pediatrics: Genetics and Metabolic Disease > Metabolic Diseases
N-Acetylglutamate Synthetase Deficiency: Differential Diagnoses & Workup
Updated: Aug 4, 2008
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
- Multimedia
Differential Diagnoses
Other Problems to Be Considered
Lysinuric protein intolerance
Reye syndrome
Workup
Laboratory Studies
- Affected newborns may experience fulminant hyperammonemia, which remains undetected unless index of suspicion is high.
- No routine laboratory tests provide definitive clues.
- The BUN level may be low, but this is an unreliable index of high blood ammonia.
- A respiratory alkalosis may be present.
- Urine orotic acid levels are within reference ranges.
- Plasma alanine and glutamine levels are elevated.
- Urine amino acids are nondiagnostic in N- acetylglutamate synthetase (NAGS) deficiency but are important in order to help rule out hyperammonemia-hyperornithinemia-homocitrullinemia (HHH) or lysinuric protein intolerance (LPI) (see Differentials).
- Urine organic acids are within reference ranges in NAGS deficiency. Ruling out organic acid disorders, which can present with similar signs and symptoms and hyperammonemia, is important.
Imaging Studies
- Imaging studies generally are not helpful, with the exception of brain imaging when cerebral edema is suspected. Documenting a finding of cerebral edema is important.
Procedures
- A liver biopsy, best performed when the patient is stable, is essential for definitive diagnosis.
- As a mitochondrial enzyme, it is quite labile; therefore, handle the specimen with scrupulous care and identify a laboratory that is capable of performing the enzymatic testing prior to scheduling the biopsy.
More on N-Acetylglutamate Synthetase Deficiency |
| Overview: N-Acetylglutamate Synthetase Deficiency |
Differential Diagnoses & Workup: N-Acetylglutamate Synthetase Deficiency |
| Treatment & Medication: N-Acetylglutamate Synthetase Deficiency |
| Follow-up: N-Acetylglutamate Synthetase Deficiency |
| Multimedia: N-Acetylglutamate Synthetase Deficiency |
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References
Caldovic L, Morizono H, Tuchman M. Mutations and polymorphisms in the human N-acetylglutamate synthase (NAGS) gene. Hum Mutat. Aug 2007;28(8):754-9. [Medline].
Bachmann C, Colombo JP, Jaggi K. N-acetylglutamate synthetase (NAGS) deficiency: diagnosis, clinical observations and treatment. Adv Exp Med Biol. 1982;153:39-45. [Medline].
Caldovic L, Morizono H, Panglao MG, et al. Late onset N-acetylglutamate synthase deficiency caused by hypomorphic alleles. Hum Mutat. Mar 2005;25(3):293-8. [Medline].
Caldovic L, Morizono H, Panglao MG, et al. Null mutations in the N-acetylglutamate synthase gene associated with acute neonatal disease and hyperammonemia. Hum Genet. Apr 2003;112(4):364-8. [Medline].
Elpeleg O, Shaag A, Ben-Shalom E, Schmid T, Bachmann C. N-acetylglutamate synthase deficiency and the treatment of hyperammonemic encephalopathy. Ann Neurol. Dec 2002;52(6):845-9. [Medline].
Elpeleg ON, Colombo JP, Amir N, et al. Late-onset form of partial N-acetylglutamate synthetase deficiency. Eur J Pediatr. Jun 1990;149(9):634-6. [Medline].
Guffon N, Schiff M, Cheillan D, et al. Neonatal hyperammonemia: the N-carbamoyl-L-glutamic acid test. J Pediatr. Aug 2005;147(2):260-2. [Medline].
Guffon N, Vianey-Saban C, Bourgeois J, et al. A new neonatal case of N-acetylglutamate synthase deficiency treated by carbamylglutamate. J Inherit Metab Dis. 1995;18(1):61-5. [Medline].
Haberle J, Koch HG. Genetic approach to prenatal diagnosis in urea cycle defects. Prenat Diagn. May 2004;24(5):378-83. [Medline].
Plecko B, Erwa W, Wermuth B. Partial N-acetylglutamate synthetase deficiency in a 13-year-old girl: diagnosis and response to treatment with N-carbamylglutamate. Eur J Pediatr. Dec 1998;157(12):996-8. [Medline].
Further Reading
Keywords
N -acetylglutamate synthetase deficiency, NAGS, NAGS deficiency, acetyl-coenzyme A, acetyl-CoA, carbamyl phosphate synthetase, CPS, hyperammonemia, urea cycle defect, anorexia, coma, apnea, respiratory failure, seizures, dysdiadochokinesia, hypothermia, respiratory alkalosis, arginase deficiency, hyperammonemia-hyperornithinemia-homocitrullinemia syndrome
Differential Diagnoses & Workup: N-Acetylglutamate Synthetase Deficiency