N-Acetylglutamate Synthetase Deficiency Workup
- Author: Karl S Roth, MD; Chief Editor: Luis O Rohena, MD more...
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- 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.
- Definitive diagnosis rests with DNA sequencing; to date, there is no newborn metabolic screen which can detect the defect.
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- 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.
See the list below:
- DNA sequencing is available in selected laboratories; mutation analysis provides a definitive diagnosis
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