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Alternative name
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Argininosuccinic acid synthetase (ASAS) deficiency
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About the condition
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Citrullinaemia 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.
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Inheritance
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Autosomal recessive
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| Year screening started in WA |
2005 |
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Incidence in Australia
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Approximately 1 in 100,000 births
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Enzyme defect
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Urea cycle disorder
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Symptoms if untreated
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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.
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Metabolites on bloodspot screening
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- Increased citrulline
- Increased citrulline/phenylalanine ratio
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Diagnostic tests
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- Plasma ammonia
- Plasma amino acids
- Urine amino and organic acids
- ASS1 gene analysis
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Treatment
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- Dialysis is sometimes needed to acutely lower the blood ammonia
- Protein-restricted diet
- Sodium benzoate and/or sodium phenylacetate
- Arginine supplementation
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Screening issues
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Citrullinaemia and argininosuccinic aciduria are the only urea cycle disorders detected by this screening strategy.
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