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Diseases

Genetic and Rare Diseases Information Center (GARD)

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Ornithine transcarbamylase deficiency


Other Names for this Disease
  • Ornithine carbamoyltransferase deficiency
  • OTC deficiency
  • OTCD
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Overview



What is ornithine transcarbamylase (OTC) deficiency?

What are the signs and symptoms of ornithine transcarbamylase (OTC) deficiency?

What causes ornithine transcarbamylase (OTC) deficiency?

How is ornithine transcarbamylase (OTC) deficiency inherited?


What is ornithine transcarbamylase (OTC) deficiency?

Ornithine transcarbamylase (OTC) 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. Mutations in the OTC gene cause OTC deficiency. OTC deficiency is an X-linked disorder.[1]
Last updated: 6/3/2011

What are the signs and symptoms of ornithine transcarbamylase (OTC) deficiency?

Ornithine transcarbamylase (OTC) deficiency often becomes evident in the first few days of life. An infant with OTC deficiency may be lacking in energy (lethargic) or unwilling to eat, and have a 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 OTC deficiency may include developmental delay and intellectual disability. Progressive liver damage, skin lesions, and brittle hair may also be seen.[1] In some affected individuals, signs and symptoms of OTC deficiency may be less severe, and may not appear until later in life.[1]
Last updated: 6/3/2011

What causes ornithine transcarbamylase (OTC) deficiency?

Ornithine transcarbamylase (OTC) deficiency is caused by mutations in the OTC gene. OTC 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 OTC 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 OTC deficiency causes neurological problems as well as eventual damage to the liver.[1]
Last updated: 3/4/2011

How is ornithine transcarbamylase (OTC) deficiency inherited?

Ornithine transcarbamylase (OTC) 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.[1]

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 OTC deficiency.[1]
Last updated: 3/4/2011

References
  1. Ornithine transcarbamylase deficiency. Genetics Home Reference (GHR). 2006; http://www.ghr.nlm.nih.gov/condition/ornithine-transcarbamylase-deficiency. Accessed 3/4/2011.