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Genetic and Rare Diseases Information Center (GARD)

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Citrullinemia type I

Other Names for this Disease
  • Argininosuccinate synthetase deficiency
  • ASS deficiency
  • Citrullinemia 1
  • Citrullinuria
  • Classic citrullinemia
More Names
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Your Question

One of my infant twins has been diagnosed with citrullinemia. Her ammonia level was very high. Do children with this condition recover from the high levels of ammonia? How is this condition treated? 

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

What happens when citrullinemia type I is not treated? 

Untreated individuals with the severe form of citrullinemia type I have hyperammonemia (plasma ammonia concentration 1000-3000 µmol/L).[1] Without prompt intervention, hyperammonemia and the accumulation of other toxic metabolites result in swelling of the brain, breathing problems, increased or decreased muscle tone, muscle weakness, problems staying warm, seizures, loss of consciousness, and sometimes death.[1][2] Without treatment, most babies die within the first few weeks of life.[2]
Last updated: 4/20/2010

How might citrullinemia type I be treated?

The treatment of citrullinemia type I should be monitored by a metabolic diseases specialist and/or a dietician. Prompt treatment is necessary to prevent the build-up of ammonia, so treatment should be initiated as soon as the diagnosis is made. Mainstays of treatment include:[2][3]

  • Low-protein diet and/or special medical foods and formula to help to avoid the build-up of ammonia
  • Medications (sodium benzoate, sodium phenylacetate and arginine) to help to reduce blood ammonia levels
  • Hemodialysis may be indicated to rapidly reduce the blood ammonia level

Long-term management includes blood tests to monitor blood levels of ammonia and amino acids which can help to make adjustments to diet and medical treatments. A physician should be contacted immediately in case of any illness.[2]  

Last updated: 4/20/2010

What happens when  citrullinemia type I is treated?

With prompt and lifelong treatment, children with citrullinemia type I can often live healthy lives with typical growth and learning. Early treatment can help prevent high ammonia levels.[2] However, even with treatment, some children may still have episodes of high ammonia. This can result in brain damage which can cause lifelong learning problems, mental retardation or spasticity.[2] Individuals often have cognitive impairment.[1] Children with the severe form (plasma ammonia levels greater than 480 µmol/L [or an initial plasma ammonia concentration greater than 300 µmol/L] who are treated promptly may survive for an indeterminate period of time, but usually have significant neurologic deficits.[1][2]


Last updated: 4/20/2010