What is it?

Ornithine transcarbamylase (OTC) deficiency is an X-linked genetic disorder that has a wide range of symptoms and severity. Babies with neonatal onset become ill within the first 30 days of life and those with late onset become ill after 30 days of age through adulthood.

What causes it?

OTC is a disorder that results from mutations (or changes) in the OTC gene, which decreases the amount of the OTC protein or changes how it works. The OTC protein is a liver enzyme that is responsible for the breakdown of ammonia, a substance formed when proteins are digested in the body. Ammonia is toxic to the brain and people with OTC deficiency can have very high levels of ammonia when they become ill with a viral infection or eat too much protein.

What are some of the common symptoms?

The severe form of OTC deficiency occurs in some affected males anywhere between 24 hours to a few days after birth, usually following a feeding that contains protein. Initial symptoms may include refusal to eat, vomiting, sleepiness, and irritability. The disorder may rapidly progress to include seizures, decreased muscle tone, and breathing problems.

If untreated, infants with the severe form of OTC deficiency may fall into coma and may potentially have intellectual disability and developmental delays.

People with milder disease may not become ill until adulthood. Adults who have OTC deficiency may exhibit headaches, nausea, difficulty forming words, decreased ability to coordinate movements, confusion, and blurred vision.

How many people have it?

About 10,000 patients worldwide are affected by OTC deficiency.

Common names for OTC1

  • Ornithine carbamoyltransferase deficiency disease

1Ornithine transcarbamylase deficiency. National Institutes of Health: Genetics Home Reference Website. https://ghr.nlm.nih.gov/condition/ornithine-transcarbamylase-deficiency#synonyms. Published October 2017. Updated March 19, 2019. Accessed March 29, 2019.2DTX 301 for OTC. Ultragenyx Pharmaceutical. https://www.ultragenyx.com/pipeline/dtx-301-for-otc/. Accessed March 28, 2019. 3 Safety and Dose-Finding Study of DTX301 (scAAV8OTC) in Adults With Late-Onset OTC Deficiency (CAPtivate). ClinicalTrials.gov. https://clinicaltrials.gov/ct2/show/NCT02991144?term=dtx+301&rank=1. Accessed April 15, 2019.

Ultragenyx Opportunities to Participate

Research plays a critical part in advancing science and treatments. Volunteers who participate in this research are essential. Future therapies would not be possible without them. Participating in clinical trials, interviews, observational studies, and disease monitoring programs help to drive research, treatment development, and disease education. It is also a way to advocate for yourself and your community. To learn more about Ultragenyx research, email [email protected].


DTX301 is an investigational gene therapy designed to address a genetic mutation in a liver enzyme which causes ammonia to build up in the bloodstream of people with OTC deficiency.2

Ultragenyx is currently enrolling a Phase 1/2 open-label, single arm, multicenter, safety and dose finding study in adults with late-onset OTC deficiency.

To be eligible to participate in this study, you should be 18 years of age or older with a diagnosis of late onset OTC deficiency that has been confirmed by enzymatic, biochemical or molecular testing and a documented history of one or more hyperammonemia events.3 This is not all of the eligibility criteria. Learn more about the DTX301 study at clinicaltrials.gov.

*These organizations are an incomplete listing of rare disease support organizations and are not controlled by, endorsed by, or affiliated with Ultragenyx Pharmaceutical Inc. The list is meant for informational purposes only and is not intended to replace your healthcare professional’s medical advice. Ask your doctor or nurse any questions you may have about your disease or treatment plan. If you would like to have your group added to the list, please contact [email protected].