Arginase Deficiency (FAQ)


The Questions and Answers that follow aim to provide an introduction to arginase deficiency for parents and other family members. Following those, we offer links to selected resources for more information and support and a list of valuable services.
Note that we use the term doctor to refer to physicians, nurse practitioners, physician assistants, and other licensed clinicians who may care for your child.
More information about many topics relevant to children with arginase deficiency and many other chronic conditions and their families can be found in the left menu. Detailed information aimed at primary care doctors can be found in our Arginase Deficiency module and the Argininemia screening page.

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 build up in the body. While the high levels of ammonia are often mild, they can be life-threatening. If untreated, developmental problems and seizures can happen.

What are the symptoms of arginase deficiency?

Infants and young children with arginase deficiency usually seem normal until age 1-4 when they start to show muscle tightness and developmental delay. Many also have microcephaly (small head due to poor brain growth).

How is it diagnosed?

Newborn screening programs test for arginase deficiency, making diagnosis possible very early in the child's life, before symptoms begin. Testing can also be done if arginase deficiency is suspected in older children.

What is the prognosis?

With treatment, the chance for a normal life is excellent, though it is not yet known whether adults with this condition will be problem-free.

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

Arginase deficiency is passed down by a child’s parents when they are both carriers of an abnormal gene for the arginase 1 enzyme. When people have just one such gene, they are called carriers and they don’t have the condition. However, people with two abnormal genes will have it. Because everyone has two copies of all of their genes, one from each parent, the chance that a child of parents who are both carriers will have arginase deficiency are 1 in 4.

What treatments/therapies/medications are recommended or available?

Treatment involves restricting protein in the diet, taking some essential amino acids, and the use of medications to remove ammonia.

How will my child’s and our family’s life be changed?

Your child will need to be on a protein-restricted food plan and take amino acids for the rest of her/his life. Some children may also need to take medication. By following treatment, it is thought that most people will lead a normal life.


Information & Support

Where can I go for further information?

For Parents and Patients


National Urea Cycle Disorders Foundation
Support and information that includes 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 a diagnosis of arginase deficiency; Screening, Technology, and Research in Genetics.

Arginase Deficiency (MedlinePlus)
Information for families that includes description, frequency, causes, inheritance, other names, and additional resources; from the National Library of Medicine.

Urea Cycle Abnormalities (Medline Plus)
Information for families that includes description, frequency, causes, inheritance, other names, and additional resources; from the National Library of Medicine.

Patient Education

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

Services for Patients & Families Nationwide (NW)

For services not listed above, browse our Services categories or search our database.

* number of provider listings may vary by how states categorize services, whether providers are listed by organization or individual, how services are organized in the state, and other factors; Nationwide (NW) providers are generally limited to web-based services, provider locator services, and organizations that serve children from across the nation.

Authors & Reviewers

Initial publication: October 2012; last update/revision: July 2019
Current Authors and Reviewers:
Author: Lynne M. Kerr, MD, PhD