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
Treatment	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.