Understanding Arginase 1 Deficiency (ARG1-D)

Helpful resources for the ARG1-D community

What is Arginase 1 Deficiency?

ARG1-D is an inherited metabolic disorder affecting children, teens, and adults, that is characterized by high levels of plasma arginine. ARG1-D is a type of urea cycle disorder (UCD) that can significantly impact the patient’s health over time.

ARG1-D Quick Facts

  • Caused by the body’s inability to break down arginine
  • High arginine levels impact a person’s ability to function
  • Symptoms typically appear between 2-4 years of age and persist through adulthood
  • In rare cases, symptoms can present after puberty

ARG1-D Symptoms

  • Muscle tightness (spasticity)
  • Missed developmental milestones
  • Intellectual delays
  • Seizures

You’re not alone. The ARG1-D community is made up of patients, caregivers, doctors, and nurses.

Girl Toxic Level

Arginine reaches unhealthy levels in ARG1-D

Boy building blocks

Symptoms typically appear at 2-4 years of age and progress

Want to learn more?

Ask your doctor if your child shows symptoms of ARG1-D

How is ARG1-D Diagnosed?

Early detection of ARG1-D is critical and can help your child get the treatment he/she needs. Symptoms typically appear at 2-4 years of age and progress.

Testing for ARG1-D is easy and usually involves a mix of:

  • Blood test for amino acids that show arginine levels
  • Genetic testing
  • Newborn screening in some states

Due to limitations of newborn screenings, ARG1-D can be missed. When that happens, people with ARG1-D may be misdiagnosed with other conditions such as cerebral palsy or hereditary spastic paraplegia.

Managing ARG1-D

The current standard of care for ARG1-D includes dietary protein restrictions, supplements, and other drugs. Although there are no FDA-approved treatments for ARG1-D that address the underlying cause of the condition, doctors may prescribe other treatments to help manage ARG1-D symptoms.

While protein restriction is effective, it is limited in its ability to reduce arginine levels to the normal range. If a protein-restricted diet is needed, consider working with a dietitian for guidance.

New treatments specifically designed to treat ARG1-D are currently being researched and tested.

Normal Protein Intake

10-53 g/day*

daily protein intake

ARG Protien intake

4-40 g/day*

ARG1-D patient
daily protein intake

* Protein intake amount varies by age and weight.

Patient Advocacy Resources

While ARG1-D is a rare condition, patients and families do not have to face this disorder alone. There is an established community of patients, caregivers, doctors and nurses who are ready to lend help and support:

Share Your Story

We love hearing from the ARG1-D community. Please reach out to us and share your experience living with or caring for someone with ARG1-D.

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