Arginase Deficiency (FAQ)

Answers to questions families often have about caring for their child with 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 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

Related Portal Content
Arginase Deficiency
Assessment and management information for the primary care clinician caring for the child with arginase deficiency.
Care Notebook
Medical information in one place with fillable templates to help both families and providers. Choose only the pages needed to keep track of the current health care summary, care team, care plan, health coverage, expenses, scheduling, and legal documents. Available in English and Spanish.

For Parents and Patients

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 a developmental Milestone Tracker app (ages 2 months to 5 years); Centers for Disease Control and Prevention.

Services for Patients & Families in New Mexico (NM)

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