This information is provided by the National Institutes of Health (NIH) Genetic and Rare Diseases Information Center (GARD).
Ornithine transcarbamylase (OTC) deficiency is a genetic disease that causes too much ammonia to accumulate in the blood (hyperammonemia). Ammonia is toxic when levels are too high and especially affects the nervous system.
Severe OTC deficiency (the early-onset form) typically affects males (and rarely females) and causes symptoms in the newborn period or early childhood. Signs and symptoms of this form may include lack of energy and appetite, poorly-controlled breathing rate and body temperature, unusual body movements, seizures, or coma. When not treated, the disease can lead to development delay, intellectual disability, and liver damage. Less frequently, symptoms of OTC deficiency begin later in life (the late-onset form) and are less severe. This form occurs in both males and females. Symptoms of this form may include episodes of delirium, erratic behavior, a reduced level of consciousness, headaches, vomiting, and seizures.
OTC is caused by mutations in the OTC gene and inheritance is X-linked. Treatment involves removing protein from the diet, taking certain medications, and having hemodialysis if needed for extremely high blood ammonia levels.
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