What is it?

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 mainly affects the nervous system. 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. This form occurs in both males and females. Genetic changes in the OTC gene cause OTC, and inheritance is X-linked.

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Signs & symptoms

OTC deficiency can have variable presentations regarding the age of onset and the severity of symptoms. In the classic and most well-known presentation, a male infant appears well initially, but by the second day of life, they are irritable, lethargic, and stops feeding. A metabolic encephalopathy develops and can progress to coma and death without treatment. Later onset forms of OTC deficiency can have variable presentations. Although late-onset forms of the disease are often considered milder than the classic infantile presentation, any affected individual is at risk for an episode of hyperammonemia that could still be life-threatening if presented with the appropriate stressors. These patients often present with headaches, nausea, vomiting, delayed growth, and various psychiatric symptoms (confusion, delirium, aggression, or self-injury).


Some infants with OTC deficiency are initially identified through newborn screening programs, but because the disorder is so rare, it is not mandatory in many states.


Treatment of an individual with OTC deficiency may require the coordinated efforts of a team of specialists. The treatment of OTC deficiency is aimed at preventing excessive ammonia from being formed or from removing excessive ammonia during a hyperammonemic episode. Long-term therapy for OTC deficiency combines dietary restrictions and the stimulation of alternative methods of converting and excreting nitrogen from the body (alternative pathways therapy).

☝️ This is not a substitute for professional medical advice. Please consult with your physician before making any medical decision.

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