Conditions Ornithine Transcarbamylase Deficiency
Ornithine transcarbamylase deficiency (OTC) is a condition in which the body is unable to process and remove the waste, ammonia. It considered an amino acid condition because ammonia is produced when the body breaks down proteins in food into their basic building blocks (amino acids). When the body’s process for removing waste is disrupted, dangerous amounts of ammonia begin to build up in the blood. This can result in severe mental disability, seizures, and a variety of other life-threatening medical problems. For the best possible outcome, early detection of OTC through newborn screening and immediate treatment are essential.
Condition Type
Amino Acid Disorders
Frequency
Ornithine transcarbamylase deficiency (OTC) affects 1 out of every 14,000 babies.
Also known as
- OTC
- Ornithine Carbamoyltransferase Deficiency Disease
- Hyperammonemia due to ornithine transcarbamylase deficiency
Follow-Up Testing
Your baby’s doctor may ask you if your baby is showing any of the signs of ornithine transcarbamylase deficiency (see Early Signs below). If your baby has certain signs, your baby’s doctor may suggest starting immediate treatment.
If your baby’s newborn screening result for ornithine transcarbamylase deficiency (OTC) was out of the normal range, your baby’s doctor or the state screening program will contact you to arrange for your baby to have additional testing. It is important to remember that an out-of-range screening result does not necessarily mean that your baby has the condition. An out-of-range result may occur because the initial blood sample was too small or the test was performed too early. However, as a few babies do have the condition, it is very important that you go to your follow-up appointment for a confirmatory test. Because the harmful effects of untreated OTC can occur soon after birth, follow-up testing must be completed as soon as possible to determine whether or not your baby has the condition.
Follow-up testing will involve checking your baby’s urine and blood samples for signs of OTC. When a child has an amino acid condition, certain substances may be present at elevated or reduced levels in the body. Measuring the amounts of these substances in your baby’s body can help doctors determine if your baby has a condition. High amounts of ammonia in the blood, low levels of the amino acids, citrulline and arginine in the blood, and high levels of orotic acid in the urine might indicate that your baby has OTC. For a definitive diagnosis, your doctor may need to order a DNA analysis or study the enzyme activity in the liver.
About Ornithine Transcarbamylase Deficiency
Early Signs
Ornithine transcarbamylase deficiency (OTC) varies widely in its severity and age of onset. Most babies develop signs of OTC within the first few days of life. However, some individuals with OTC may not show any signs or symptoms until later in life. These later onset cases are usually less severe than those that develop in infancy.
Early signs of OTC include:
- Developmental delays
- Poor appetite
- Sleeping longer or more often
- Tiredness
- Irritability
- Vomiting
- Trouble breathing
- Involuntary or uncontrolled body movements
- Trouble regulating body temperature (your baby might get hot or cold easily)
If your baby shows any of these signs, be sure to contact your baby’s health care provider immediately.
Treatment
Dietary Treatments
Your baby may need to be on a low-protein diet in order to avoid the proteins that their body cannot break down. A dietician or a nutritionist can help you plan a healthy diet for your baby.
Your baby’s doctor might also recommend special formulas and foods for children with ornithine transcarbamylase deficiency (OTC). These formulas will likely need to continue through adulthood.
Supplements and Medications
Your baby’s health care provider may prescribe supplements to help your baby’s body get rid of excess ammonia in the blood. Everyone has some ammonia in their blood, but high levels can be toxic.
Dialysis
Some babies with OTC may require dialysis to lower the levels of ammonia in their bodies. Dialysis is a treatment that uses a special machine to filter harmful wastes, salt, and excess fluid from the blood.
Expected Outcomes
When ornithine transcarbamylase deficiency (OTC) is detected early and proper treatment is started immediately, many babies with the condition are able to live longer lives with improved growth and development. This is why newborn screening for OTC is so important.
When we eat food, our bodies break down proteins into a form that can be used by our cells. During this process, a waste product, called ammonia, is produced. Ammonia is processed and removed from the body through the action of several different enzymes. In ornithine transcarbamylase deficiency (OTC), the enzyme ornithine carbamoyltransferase is not working correctly.
Babies with OTC either do not make enough or make non-working copies of ornithine transcarbamylase. When ornithine transcarbamylase does not work correctly, the body cannot remove ammonia through the urine. This causes a dangerous build-up of ammonia in the body.
OTC is an X-linked recessive genetic condition. This means that males are affected more often than females, and that a male must inherit one copy of the non-working gene from his mother to have the condition. In most cases, a female must inherit two copies of the non-working gene, one from each parent, in order to have the condition. Sometimes, females with one non-working copy of the gene can express symptoms associated with the condition. While having a child with OTC is rare, when one or both parents carry the non-working gene, they can have more than one child with the condition. Learn more about X-linked recessive inheritance.
Unfortunately, even with treatment, some children may experience learning disabilities, intellectual disabilities, or tight muscles (spasticity), which are commonly associated with OTC.Children who do not receive treatment for OTC are at risk for severe intellectual disability, seizures, coma, or even death.
Causes
When we eat food, our bodies break down proteins into a form that can be used by our cells. During this process, a waste product, called ammonia, is produced. Ammonia is processed and removed from the body through the action of several different enzymes. In ornithine transcarbamylase deficiency (OTC), the enzyme ornithine carbamoyltransferase is not working correctly.
Babies with OTC either do not make enough or make non-working copies of ornithine transcarbamylase. When ornithine transcarbamylase does not work correctly, the body cannot remove ammonia through the urine. This causes a dangerous build-up of ammonia in the body.
OTC is an X-linked recessive genetic condition. This means that males are affected more often than females, and that a male must inherit one copy of the non-working gene from his mother to have the condition. In most cases, a female must inherit two copies of the non-working gene, one from each parent, in order to have the condition. Sometimes, females with one non-working copy of the gene can express symptoms associated with the condition. While having a child with OTC is rare, when one or both parents carry the non-working gene, they can have more than one child with the condition. Learn more about X-linked recessive inheritance.
Support for Ornithine Transcarbamylase Deficiency
Support Services
Support groups can help connect families who have a child or other family member affected with ornithine transcarbamylase deficiency (OTC) with a supportive community of people who have experience and expertise in living with the condition. These organizations offer resources for families, affected individuals, health care providers, and advocates:
Accessing Care
Work with your baby’s health care provider to determine the next steps for your baby’s care. Your baby’s doctor may help you coordinate care with a physician that specializes in metabolism, a dietician who can help plan your child’s specialized diet, and other medical resources in your community. Some children with ornithine transcarbamylase deficiency (OTC) have developmental delays. If you think that your baby is not meeting their developmental milestones, ask your baby’s doctor about the next steps in accessing a developmental evaluation and care.
Because OTC is a genetic condition, you may want to talk with a genetics specialist. A genetic counselor or geneticist can help you understand the causes of the condition, discuss genetic testing for OTC, and understand what this diagnosis means for other family members and future pregnancies. Speak with your baby’s doctor about getting a referral. The Clinic Services Search Engine offered by the American College of Medical Genetics and Genomics (ACMG) and the Find a Genetic Counselor tool on the National Society of Genetic Counselors (NSGC) website are two good resources for you or your baby's health care provider to use to identify local specialists.
Families' Experiences
Brooke's mother discovered she was a carrier of ornithine transcarbamylase deficiency (OTC) after her first son passed away from metabolic disorder. When Brooke was born, she was also diagnosed with OTC. She lived a relatively healthy childhood, but was in and out of the hospital with high ammonia levels. However, she did suffer from a hyperammonia attack and was transported to the ICU, where she spent her 15th birthday. Read more about Brooke's experience and her ability to stay positive through her journey.
References & Sources
Visit MedlinePlus Genetics for more condition information
Visit OMIM to search its online catalog of human genes and disorders
Visit Healthline to learn more about congenital urea cycle disorders
ACT Sheets
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