Argininosuccinic aciduria

Alternative names
  • Argininosuccinic acid lyase (ASAL) deficiency
  • Argininosuccinase deficiency
About the condition Argininosuccinic aciduria is an amino acid disorder. It is caused by a missing enzyme from the urea cycle. Infants with this disorder are not able to convert ammonia into urea. Ammonia accumulates in the body and is toxic to the brain. Ammonia is a waste-product and is normally produced during the breakdown of protein from food or muscle.
Inheritance Autosomal recessive
Year screening started in WA 2005
Incidence in Australia Approximately 1 in 100,000 births
Enzyme defect Urea cycle disorder
Symptoms if untreated This disorder usually causes toxic levels of blood ammonia in the first days of life. This can lead to vomiting, lethargy, seizures, coma and death. There are also some less severe forms, which can cause intellectual disability and may go undetected for months or years. Children with this disorder may also develop brittle hair called trichorrhexis nodosa.
Metabolites on bloodspot screening
  • Increased citrulline
  • Increased argininosuccinate
Diagnostic tests
  • Plasma ammonia
  • Plasma amino acids
  • Urine amino and organic acids
  • ASL gene analysis
  • Dialysis is sometimes needed to acutely lower the blood ammonia
  • Protein-restricted diet
  • Sodium benzoate and/or sodium phenylacetate
  • Arginine supplementation
Screening issues Citrullinaemia and argininosuccinic aciduria are the only urea cycle disorders detected by this screening strategy.