Living with Hyperammonemia, type III
An inherited condition, also called N-acetylglutamate synthase deficiency, in which ammonia builds up in the blood and affects the brain.
Understanding Hyperammonemia, type III
Ammonia forms when proteins break down and is harmful in high amounts, especially to the brain. In infants, signs often appear in the first few days of life. In some people, signs do not appear until later. Some adults notice that high-protein foods affect how they feel. Illness or stress can trigger episodes of vomiting, poor coordination, headaches, confusion, or behavior changes.
Signs & symptoms
Symptoms vary from person to person. GARD lists these among the most common:
- Floppy, low muscle tone in infants
- Nausea
- Vomiting
- Low energy (lethargy)
- Not wanting to eat
- Trouble controlling breathing or body temperature
Not everyone has every symptom. GARD's list comes from the Human Phenotype Ontology.
Diagnosis
- 1Talk with your doctor
Share the symptoms you've noticed, when they started and your family health history. Notes and photos can help.
- 2See a specialist
Specialists who may be involved include brain and nervous system specialists and genetic specialists.
- 3Consider genetic testing
Changes in NAGS are linked to this condition. Genetic testing and counseling can help confirm a diagnosis and explain what it means for your family.
Care & treatment
- Care team
- Brain and nervous system specialists (neurologists); Genetic specialists (geneticists)
- Expert care
- Ask about multidisciplinary care centers for rare conditions
- Treatment
- GARD doesn't list specific treatments for this condition. Your care team will tailor care to your symptoms.
- Research
- Clinical trials and observational studies may be options. See the research section below.
General information, not medical advice. Your care team makes the decisions.
Everyday life
Living with a rare condition is easier with support.
- Connect with National Urea Cycle Disorders Foundation
- Keep notes on symptoms, changes and questions for appointments
- Ask about patient registries that help research
- Look into financial aid and travel resources for care visits
Quick facts
Changes in the NAGS gene cause this condition. It is autosomal recessive, so a child inherits a changed copy of the gene from each parent.
Also known as: amino acid acetyltransferase deficiency; congenital aga deficiency; hyperammonemia due to n-acetylglutamate synthase deficiency; n-acetylglutamate synthase deficiency; n-acetylglutamate synthetase deficiency; n-acetylglutamate transferase deficiency
Patient organizations
- National Urea Cycle Disorders FoundationHyperammonemia, type III · United States
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