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Citrullinemia, type I

(SIT-ruh-luh-NEE-mee-uh • type • 1)

General Condition Information

Other Names

  • Argininosuccinate synthetase deficiency (Citrullinemia)
  • Arginosuccinate synthetase deficiency (Citrullinemia)
  • Citrullinemia
  • Citrullinemia I
  • Citrullinemia I (ASA synthetase def)
  • Citrullinemia type I
  • Citrullinemia type I (Argininosuccinate synthetase deficiency)
  • Citrullinemia type I (argininosuccinate synthetase)
  • Citrullinemia, type 1 or ASA Synthetase deficiency
  • Citrullinemia, type I or ASA Synthetase deficiency

Condition Type

Birth Prevalence

  • It is estimated that less than 80 babies are born with this condition each year in the United States.
  • It is more common in babies of Northern European descent.
  • Visit GeneReviews to learn more about how often this condition occurs.

Screening Finding

Increased citrulline

What is Citrullinemia, type I

Citrullinemia, type I is an inherited (genetic) condition that prevents the body from removing ammonia properly. Ammonia is a waste product produced when the body breaks down protein.

Citrullinemia, type I occurs when an enzyme called arginosuccinate synthase I doesn’t work correctly. You need arginosuccinate synthase I for a process in your body called the urea cycle. The urea cycle helps remove ammonia from the body. 

In citrullinemia, type I, this enzyme is missing or is not made correctly. If your baby doesn’t have enough working arginosuccinate synthase I enzyme, ammonia builds up.

High levels of ammonia are very toxic to the body, especially the brain and nerves. If untreated, damage to the brain and nerves leads to the signs and symptoms of the condition. In severe cases, this condition can lead to coma or death if not treated early.

Newborn Screening and Follow-Up

Condition Details

Treatment and Management

It is important to talk to your health care provider about which treatment(s) are best for your baby. The goal of treatment is to prevent the health problems caused by this condition. 

Treatments may include the following:

  • Drugs that help remove ammonia from the body
  • Diet low in protein
  • Arginine supplements to help lower ammonia levels
  • Liver transplant

Children who receive early and ongoing treatment for citrullinemia, type I can have healthy growth and development.

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