General Condition Information
- Citrullinemia II
- Citrullinemia type II
- Citrullinemia, type II (Citron deficiency)
- 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 Citrullinemia, type II
Citrullinemia, type II is an inherited (genetic) condition that prevents the body from removing ammonia properly. Ammonia is produced when the body breaks down proteins.
Citrin is a protein needed for a process in your body called the urea cycle. The urea cycle helps remove ammonia from the body. Citrin is also important for your liver to work properly and helps your body break down carbohydrates to make energy.
In citrullinemia, type II, citrin is missing or is not made correctly. If your baby does not have enough working citrin protein, the urea cycle in their body does not work well and ammonia builds up.
The buildup of ammonia, poor digestion of carbohydrates, and problems with your baby’s liver lead to the signs and symptoms of the condition.
Newborn Screening and Follow-Up
Newborn screening for citrullinemia, type II is done using a small amount of blood collected from your baby’s heel. To learn more about this process, visit the Blood Spot Screening page.
During screening, a special machine measures how much of a substance called citrulline is in your baby’s blood. When the urea cycle is not working well, citrulline builds up. Babies with high levels of citrulline might have citrullinemia, type II.
If your baby’s blood spot screening result for citrullinemia, type II 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/or 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 have serious health problems if they are not diagnosed and treated quickly.
False-positive newborn screening results for this condition are rare. However, screening samples collected too early (before the baby is 24 hours old) may affect the results of screening.
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 to get 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 citrullinemia, type II can appear any time from birth to adulthood. Eating foods the body cannot break down properly, illness, infection, or a long time without food can all trigger citrullinemia, type II symptoms.
Signs of the condition may include the following:
The condition is caused by a change in the SLC25A13 gene. This gene gives your body instructions for making the protein citrin. Citrin helps break down sugars, make proteins, and get rid of toxins in your body.
Without a working SLC25A13 gene, your baby’s body cannot make citrin correctly. Their body cannot get rid of ammonia, which builds up in the body. They have trouble digesting foods that are high in carbohydrates, like bread or sugary treats. Their liver also has trouble working the way it should.
- Citrullinemia, type II is an autosomal recessive condition. Babies inherit it when each parent passes down a nonworking SLC25A13 gene to their baby. Only babies with two nonworking SLC25A13 genes—one from the mom and one from the dad—have this condition.
- People with one working copy and one nonworking copy of the SLC25A13 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 SLC25A13 gene, they have a 1 in 4 chance of having a child with citrullinemia, type II.
- Carriers for citrullinemia, type II 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 citrullinemia, type II.
- Parents who already have a child with citrullinemia, type II still have a 1 in 4 chance of having another child with citrullinemia, type II. 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:
- Special formulas, vitamins, and supplements
- Low-carbohydrate diet
- Arginine supplements to lower ammonia levels
- Liver transplant
Children who receive early and ongoing treatment for citrullinemia, type II can have healthy growth and development.