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Ornithine transcarbamylase deficiency
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Reviewed June 2006
What is ornithine transcarbamylase deficiency?
Ornithine transcarbamylase deficiency is an inherited disorder that causes ammonia to accumulate in the blood. Ammonia, which is formed when proteins are broken down in the body, is toxic if the levels become too high. The nervous system is especially sensitive to the effects of excess ammonia.
Ornithine transcarbamylase deficiency often becomes evident in the first few days of life. An infant with ornithine transcarbamylase deficiency may be lacking in energy (lethargic) or unwilling to eat, and have poorly-controlled breathing rate or body temperature. Some babies with this disorder may experience seizures or unusual body movements, or go into a coma. Complications from ornithine transcarbamylase deficiency may include developmental delay and intellectual disability. Progressive liver damage, skin lesions, and brittle hair may also be seen.
In some affected individuals, signs and symptoms of ornithine transcarbamylase may be less severe, and may not appear until later in life.
How common is ornithine transcarbamylase deficiency?
Ornithine transcarbamylase deficiency is believed to occur in approximately 1 in every 80,000 people.
What genes are related to ornithine transcarbamylase deficiency?
Mutations in the OTC gene cause ornithine transcarbamylase deficiency.
Ornithine transcarbamylase deficiency belongs to a class of genetic diseases called urea cycle disorders. The urea cycle is a sequence of reactions that occurs in liver cells. It processes excess nitrogen, generated when protein is used by the body, to make a compound called urea that is excreted by the kidneys.
In ornithine transcarbamylase deficiency, the enzyme that starts a specific reaction within the urea cycle is damaged or missing. The urea cycle cannot proceed normally, and nitrogen accumulates in the bloodstream in the form of ammonia.
Ammonia is especially damaging to the nervous system, so ornithine transcarbamylase deficiency causes neurological problems as well as eventual damage to the liver.
Read more about the OTC gene.
How do people inherit ornithine transcarbamylase deficiency?
Ornithine transcarbamylase deficiency is an X-linked disorder. A condition is considered X-linked if the mutated gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes. A characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.
In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. In females (who have two X chromosomes), mutations in both copies of the gene will cause the disorder. Some females with only one altered copy of the OTC gene also show signs and symptoms of ornithine transcarbamylase deficiency.
Where can I find information about diagnosis or management of ornithine transcarbamylase deficiency?
These resources address the diagnosis or management of ornithine transcarbamylase deficiency and may include treatment providers.
General information about the diagnosis and management of genetic conditions is available in the Handbook. Read more about genetic testing, particularly the difference between clinical tests and research tests.
To locate a healthcare provider, see How can I find a genetics professional in my area? in the Handbook.
Where can I find additional information about ornithine transcarbamylase deficiency?
You may find the following resources about ornithine transcarbamylase deficiency helpful. These materials are written for the general public.
You may also be interested in these resources, which are designed for healthcare professionals and researchers.
What other names do people use for ornithine transcarbamylase deficiency?
What if I still have specific questions about ornithine transcarbamylase deficiency?
Where can I find general information about genetic conditions?
The Handbook provides basic information about genetics in clear language.
These links provide additional genetics resources that may be useful.
What glossary definitions help with understanding ornithine transcarbamylase deficiency?
ammonia ; cell ; chromosome ; class ; coma ; compound ; deficiency ; developmental delay ; disability ; enzyme ; gene ; hyperammonemia ; inheritance ; inherited ; lacking in energy ; lethargic ; nervous system ; neurological ; newborn screening ; protein ; screening ; sex chromosomes ; toxic ; urea
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
See also Understanding Medical Terminology.
References (6 links)
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook.