Carbamoyl phosphate synthetase I deficiency
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Reviewed February 2013
What is carbamoyl phosphate synthetase I deficiency?
Carbamoyl phosphate synthetase I deficiency is an inherited disorder that causes ammonia to accumulate in the blood (hyperammonemia). Ammonia, which is formed when proteins are broken down in the body, is toxic if the levels become too high. The brain is especially sensitive to the effects of excess ammonia.
In the first few days of life, infants with carbamoyl phosphate synthetase I deficiency typically exhibit the effects of hyperammonemia, which may include unusual sleepiness, poorly regulated breathing rate or body temperature, unwillingness to feed, vomiting after feeding, unusual body movements, seizures, or coma. Affected individuals who survive the newborn period may experience recurrence of these symptoms if diet is not carefully managed or if they experience infections or other stressors. They may also have delayed development and intellectual disability.
In some people with carbamoyl phosphate synthetase I deficiency, signs and symptoms may be less severe and appear later in life.
How common is carbamoyl phosphate synthetase I deficiency?
Carbamoyl phosphate synthetase I deficiency is a rare disorder; its overall incidence is unknown. Researchers in Japan have estimated that it occurs in 1 in 800,000 newborns in that country.
What genes are related to carbamoyl phosphate synthetase I deficiency?
Mutations in the CPS1 gene cause carbamoyl phosphate synthetase I deficiency. The CPS1 gene provides instructions for making the enzyme carbamoyl phosphate synthetase I. This enzyme participates in the urea cycle, which is a sequence of biochemical reactions that occurs in liver cells. The urea cycle processes excess nitrogen, generated when protein is broken down by the body, to make a compound called urea that is excreted by the kidneys. The specific role of the carbamoyl phosphate synthetase I enzyme is to control the first step of the urea cycle, a reaction in which excess nitrogen compounds are incorporated into the cycle to be processed.
Carbamoyl phosphate synthetase I deficiency belongs to a class of genetic diseases called urea cycle disorders. In this condition, the carbamoyl phosphate synthetase I enzyme is at low levels (deficient) or absent, and the urea cycle cannot proceed normally. As a result, nitrogen accumulates in the bloodstream in the form of toxic ammonia instead of being converted to less toxic urea and excreted. Ammonia is especially damaging to the brain, and excess ammonia causes neurological problems and other signs and symptoms of carbamoyl phosphate synthetase I deficiency.
Read more about the CPS1 gene.
How do people inherit carbamoyl phosphate synthetase I deficiency?
This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.
Where can I find information about diagnosis or management of carbamoyl phosphate synthetase I deficiency?
These resources address the diagnosis or management of carbamoyl phosphate synthetase I deficiency and may include treatment providers.
- Baby's First
- Gene Review: Urea Cycle
- Genetic Testing Registry: Congenital hyperammonemia, type
- MedlinePlus Encyclopedia: Hereditary Urea Cycle
You might also find information on the diagnosis or management of carbamoyl phosphate synthetase I deficiency in Educational resources and Patient support.
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 carbamoyl phosphate synthetase I deficiency?
You may find the following resources about carbamoyl phosphate synthetase I 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 carbamoyl phosphate synthetase I deficiency?
- carbamoyl-phosphate synthase I deficiency disease
- carbamyl-phosphate synthetase I deficiency disease
- congenital hyperammonemia, type I
What if I still have specific questions about carbamoyl phosphate synthetase I deficiency?
Where can I find general information about genetic conditions?
The Handbook provides basic information about genetics in clear language.
- What does it mean if a disorder seems to run in my family?
- What are the different ways in which a genetic condition can be inherited?
- If a genetic disorder runs in my family, what are the chances that my children will have the condition?
- Why are some genetic conditions more common in particular ethnic groups?
These links provide additional genetics resources that may be useful.
What glossary definitions help with understanding carbamoyl phosphate synthetase I deficiency?
ammonia ; autosomal ; autosomal recessive ; cell ; class ; coma ; compound ; congenital ; deficiency ;disability ; enzyme ; gene ; hyperammonemia ; incidence ; neurological ; newborn screening ; phosphate ;protein ; recessive ; screening ; toxic ; urea
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
See also Understanding Medical Terminology.
References (9 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.