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 the it works. The OTC protein is a liver enzyme that is responsible for the metabolism of ammonia, a substance formed when proteins are broken down 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, lethargy, 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 OTC deficiency may not become ill until adulthood. Adults who have OTC deficiency may exhibit migraines, nausea, difficulty forming words, decreased ability to coordinate movements, confusion, hallucinations, 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.

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