Arginase Deficiency


Here you’ll find answers to some of the questions that parents often have about this condition. Additional resources are listed at the bottom of the page. Diagnosis and management information can be found in the Arginase Deficiency module, which is written for primary care clinicians but also may be of help to parents and family members. Information can also be found in the Argininemia Newborn Screening Page. See Arginase Deficiency.

What is arginase deficiency and what causes it?

Arginase deficiency is a rare genetic disorder. It results from the absence of the enzyme arginase 1, which causes ammonia to be built up in the body. Although the hyperammonemia is usually mild, it can be life-threatening. Infants and young children with this disorder usually appear completely normal until age 1-4 when they begin to show spasticity and developmental delay. Many also develop microcephaly. If untreated developmental regression and seizures occur in the majority of individuals.

What are the symptoms of arginase deficiency?

Although babies are usually normal at birth, over time they begin showing signs of developmental delay and then abnormal movements due to increased muscle tone, called spasticity. Seizures may also occur.

How is it diagnosed?

In the United States, arginase deficieny is one of the conditions tested for by newborn screening, and diagnosis is made very early on in the child's life, before symptoms occur. In older children suspected of having arginase deficiency, biochemical and genetic testing is performed to confirm the diagnosis.

What is the prognosis?

With treatment, which is dietary restriction of certain amino acids, the prognosis for a normal life is likely excellent, although there is not enough evidence to tell us that adult individuals with this condition will be completely problem-free.

What is the risk to other family members and future babies?

Arginase deficiency is inherited in an autosomal recessive manner; this means each future child has a 1 in 4 chance of having the disorder, a 2 in 4 chance of being a carrier for this condition, and a 1 in 4 chance of not having the mutated gene.

What treatments/therapies/medications are recommended or available?

Treatment is by dietary protein restriction, supplementation of essential amino acids, and the use of alternative pathways (sodium phenylbutyrate and/or benzoate) to remove the nitrogen waste.

How will my child and our family be impacted?

Your child will need to be on a protein-restricted diet for life, with amino-acid supplementation to make sure that amino-acid needs are being met. Some individuals may also need to be on medication. However, with good adherence to treatment, it is thought that most individuals will lead a normal life. This condition is quite rare and individuals have not been followed for a long enough time to determine if there will be problems for adults in the future, even with treatment as currently understood.


Information & Support

Where can I go for further information?

For Parents and Patients


National Urea Cycle Disorders Foundation
This non-profit organization provides support services and information for families; medical lectures on urea cycle disorders; nutrition and medication resources; and information about events and conferences.


Argininemia - Information for Parents (STAR-G)
A fact sheet, written by a genetic counselor and reviewed by genetic specialists, for families who have received an initial diagnosis of a newborn disorder; Screening, Technology, and Research in Genetics.

Argininemia (Genetics Home Reference)
Excellent, detailed review of condition for patients and families; sponsored by the U.S. National Library of Medicine.

Urea Cycle Abnormalities (Medline Plus)
Contains information for families about urea cycle disorders in general; arginase deficiency is one of these.

Genetics in Primary Care Institute (AAP)
The goal of this site is to increase collaboration in the care of children with known or suspected genetic disorders. It includes health supervision guidelines and other useful resources; represents a collaboration among the Health Resources & Services Administration, the Maternal and Child Health Bureau, and the American Academy of Pediatrics.

National Newborn Screening & Global Resource Center (NNSGRC)
Fact sheets, data reports, publications, and information for clinicians about genetic screening that includes links to state genetic contacts.

Patient Education

Learn the Signs. Act Early (CDC)
Tools, videos, lists, and learning materials to track a child’s development (ages 2 months to 5 years) and act if concerned about progress; Centers for Disease Control and Prevention.


Newborn Screening Programs

See all Newborn Screening Programs services providers (22) in our database.

Nutrition, Metabolic

See all Nutrition, Metabolic services providers (1) in our database.

Pediatric Genetics

See all Pediatric Genetics services providers (3) in our database.

Pediatric Metabolic Genetics

See all Pediatric Metabolic Genetics services providers (1) in our database.

For other services related to this condition, browse our Services categories or search our database.

Authors & Reviewers

Initial Publication: October 2012; Last Update: October 2015
Current Authors and Reviewers (click on name for bio):