General Condition Information
- Hyperornithinemia-hyperammonemia-homocitrullinuria syndrome
- It is unknown how many babies are born with this rare condition each year in the United States.
- Visit GeneReviews to learn more about how often this condition occurs.
What is Ornithine Translocase Deficiency
Ornithine translocase deficiency is an inherited (genetic) condition that prevents the body from breaking down a substance in the blood called ornithine. Ornithine is an amino acid, one of the building blocks that makes up proteins.
Mitochondrial ornithine transporter 1 is a protein that helps your body transport ornithine. Ornithine is used in a bodily process called the urea cycle. The urea cycle helps remove a waste product called ammonia from the body. The body produces ammonia by breaking down proteins. Ornithine also helps make sure that the body has the right balance of other amino acids in the body to properly produce proteins.
If your baby does not have enough working mitochondrial ornithine transporter 1, they can have trouble breaking down ornithine and getting rid of ammonia. High amounts of ornithine and ammonia can damage your baby’s brain and body. If untreated, this damage leads to the signs and symptoms of the condition.
Newborn Screening and Follow-Up
Newborn screening for ornithine translocase deficiency requires collecting a small amount of blood from your baby’s heel. To learn more about this process, visit the Blood Spot Screening page.
Screening measures how much ornithine is in your baby’s blood. Babies with high levels of ornithine might have ornithine translocase deficiency.
If your baby’s blood spot screening result for ornithine translocase deficiency is out-of-range, your baby’s health care provider will contact you. Together, you will discuss next steps and follow-up plans.
An out-of-range screening result does not mean that your baby definitely has the condition. It does mean that your baby needs more follow-up testing. To learn more about screening results, visit the Blood Spot Screening Results page.
Your baby may need the following tests after an out-of-range screening result:
- Blood and urine tests
- Genetic testing using a blood sample
You should complete any recommended follow-up testing as soon as possible. Babies with this condition can develop serious problems in infancy if they are not diagnosed and treated quickly.
False-positive newborn screening results for this condition can happen.
Newborn screening helps babies lead healthier lives. If your baby has an out-of-range result, follow up with your health care provider quickly. It is important to follow their instructions. Your baby may need treatment right away, even if they are not showing signs or symptoms. In some cases, your baby’s health care provider may decide it is best to watch (monitor) your baby to decide next steps. Careful monitoring and early treatment will help your baby stay as healthy as possible.
Signs of ornithine translocase deficiency can vary widely and may appear anytime from infancy to childhood. These signs may be triggered by eating foods high in protein, going a long time without eating (prolonged fasting), illnesses, and infections.
Signs of the condition may include the following:
A change in the SLC25A15 gene causes this condition. This gene gives the body instructions for making the protein mitochondrial ornithine transporter 1. This protein helps transport the amino acid ornithine for use in the urea cycle.
Without a working SLC25A15 gene, the body cannot break down ornithine. As a result, ornithine and related substances (ammonia) can build up and damage the brain and body.
- Ornithine translocase deficiency is an autosomal recessive condition. Babies inherit the condition when each parent passes down a nonworking SLC25A15 gene to their baby. Only babies with two nonworking SLC25A15 genes—one from the mom and one from the dad—have this condition.
- People with one working copy and one nonworking copy of the SLC25A15 gene are called carriers.
- Carriers do not have or develop the condition. However, they may pass down a nonworking copy of the gene to their children.
- If two parents are carriers of a nonworking copy of the SLC25A15 gene, they have a 1 in 4 chance of having a child with ornithine translocase deficiency.
- Carriers for ornithine translocase deficiency often do not know they are carriers before having a child with the condition. In most cases, families have no history of the condition until the birth of a child with ornithine translocase deficiency.
- Parents who already have a child with ornithine translocase deficiency still have a 1 in 4 chance of having another child with ornithine translocase deficiency. This 1 in 4 chance stays the same for all future children.
- Genetic counselors and medical geneticists can help families learn about this condition and the chance of having children with it. Visit the National Society of Genetic Counselors to find a genetic counselor and the American College of Medical Genetics and Genomics to find a medical geneticist.
Treatment and Management
It is important to talk to your health care provider about which treatment(s) are best for your baby. The goal of treatment is to prevent the health problems caused by this condition.
Treatments may include the following:
- Diet low in certain proteins
- Special formula or food
- Supplements or medications
Children who receive early and ongoing treatment for ornithine translocase deficiency can lead healthier lives.