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CPS I Deficiency

Medical information you need to know as an adult with CPS I deficiency

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Overview of the Condition:

CPS I deficiency is a rare metabolic condition in which a chemical called carbamoyl phosphate synthetase does not work correctly in your body. This can cause ammonia to build up in your blood over time. When ammonia builds up too much, it can cause serious health problems. You can manage CPS I deficiency throughout your life with a special low-protein diet, drug therapy, and ongoing health care.

CPS I deficiency is also sometimes called carbamoyl phosphate synthetase I deficiency.

Medical Problems for Babies and Children:

  • If CPS I deficiency goes undetected, babies and children may have: extreme sleepiness, irritability, vomiting, poor appetite, trouble with breathing or body temperature, unusual body movements, seizures, or coma.  These symptoms can be triggered by eating a lot of protein, or after an illness or surgery, or by steroid medication.
  • If untreated, developmental problems for babies and children with CPS I deficiency can include delayed growth or learning delays.
  • Newborns in some US states are now tested for CPS I deficiency. If the condition is identified early and treatment and diet are followed carefully, many of these health problems can be prevented.

Medical Problems for Teens and Young Adults:

  • Teens and young adults with CPS I deficiency may have learning disabilities.
  • If you have an illness, fever, surgery, or are pregnant, contact your health-care provider right away.
  • Watch for signs of ammonia build-up (also called hyperammonemia) including: nausea, vomiting, sleepiness, or unusual problems with your mood or thinking. If you have any of these, get medical care right away.
  • Some teens and young adults with CPS I deficiency have anxiety or depression. Counseling and medication can help. If you have anxiety or depression, it is important to get in touch with your health care provider to get treatment.

How to Minimize Medical Problems and Complications:

Fertility and Pregnancy:

  • CPS I deficiency does not affect your ability to have children.
  • Genetic counseling can help you and your partner understand the risks to your children. Your doctor can refer you to a genetic counselor who has a special understanding of your health issues.
  • Pregnant women with CPS I deficiency must follow a careful diet with special guidance from a dietician and health care providers.

How To Get Support:

  • Get education support from teachers and specialists at your school.
  • Join a support group with people who have CPS I deficiency or similar metabolic conditions. This group of health conditions is called urea cycle disorders.
  • A lot of research is being done on CPS I deficiency and other urea cycle disorders. Get up-to-date information about new treatments and discoveries at the Urea Cycle Foundation website: http://nucdf.org/


AAP/AAFP/ACP Transition Clinical Report

Transition Toolkit (New England Consortium of Metabolic Programs)

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National Urea Cycle Disorders Foundation

Acute Illness Protocol for CPS I Deficiency

National Institutes of Health – Genetics Home Reference – CPS I Deficiency

Genetics Referrals:

Clinical Services

Genetic Services

What Next?

Now you can fill out the Medical Health Summary, print it, and save it. This will help you keep important medical information in one place.


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This Metabolic Condition Basics guide was adapted with permission from the American College of Medical Genetics ACT Sheet

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