Conditions Citrullinemia, Type II

Citrullinemia, type II (CIT II) is a condition in which the body is unable to make citrin, a protein that helps move substances within the cells. These substances are important for breaking down sugars, producing proteins and nucleotides, and allowing for the normal function of the liver. CIT II is considered an amino acid condition because people with this condition are unable to transport certain amino acids into mitochondria, the energy-production centers of the cell. You may also hear CIT II called a urea cycle condition. This name is used to describe conditions that cause ammonia to accumulate in the bloodstream.

CIT II is not the same condition as citrullinemia, type I. Even though these conditions have similar names, they have different signs, outcomes, and treatments. If you are looking for information about citrullinemia, type I, go to this page.

Condition Type

Amino Acid Disorders


Citrullinemia, type II (CIT II) is most common in the Japanese population, where it affects one out of every 100,00 to 230,000 individuals. CIT II has also been reported in people from other parts of East Asia and from the Middle East.

Also known as

  • CIT II
  • Citrullinuria
  • Citrin deficiency
  • Neonatal intrahepatic cholestasis caused by citrin deficiency (neonatal form only)
  • NICCD (neonatal form only)
  • Citrullinemia

Follow-Up Testing

Your baby’s doctor may ask you if your baby is showing any of the signs of CIT II (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 citrullinemia (CIT II) 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 child 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 CIT II 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 citrullinemia. Harmful amounts of certain substances build up in the body when a child has an amino acid condition, so measuring the amounts of these substances in your baby’s body can help doctors determine if your baby has a condition. High amounts of citrulline in the blood might indicate that your baby has CIT II. Sometimes follow-up testing may also include testing a very small sample of skin.

About Citrullinemia, Type II

Early Signs

Signs of citrullinemia type II (CIT-II) can begin in infancy, adolescence, and adulthood. In babies, the signs of CIT-II usually begin between one and five months of age.

Babies with CIT-II show signs of:

  • Yellowish skin and eyes (known as jaundice)
  • Low birth weight
  • Delayed growth
  • Low blood sugar (called hypoglycemia)

Some of these signs may be seen especially when babies with CIT-II eat foods that their bodies cannot break down. They can be triggered by long periods of time without eating, illnesses, and infections.

If your baby shows any of these signs, be sure to contact your baby’s doctor immediately.

For information on signs of CIT-II in adolescents and adults, check out this link.


Dietary Treatments

Babies with citrullinemia type II (CIT-II) are often treated with a change to a low-carbohydrate diet. A nutritionist or dietician familiar with CIT-II can help you plan an appropriate diet for your child.

Supplements and Medication

Your baby’s doctor may prescribe arginine supplements. Arginine is a substance naturally found in proteins, which can help lower ammonia levels in the blood. Everyone has some ammonia in their blood, but CIT-II can cause dangerously high levels, and high ammonia levels can be toxic. Your baby’s doctor can write you a prescription for these supplements.

Expected Outcomes

In babies, citrullinemia type II (CIT-II) will often resolve itself. Signs of CIT-II disappear until adolescence or adulthood. In adults, treatment can reduce the signs of CIT-II.

CIT-II may cause severe liver problems. If untreated, adults are at risk of needing a liver transplant.


When we eat food, our bodies use a series of enzymes to break it down. Some of these enzymes help move nutrients within the cell. Citrin is one such enzyme. Citrin helps break down carbohydrates and transport certain amino acids, which are the building blocks of proteins.

If your baby has citrullinemia, type II (CIT-II), then their body either does not make enough or makes non-working citrin. When citrin does not work properly, your baby’s body cannot break down carbohydrates correctly. It causes low sugar levels, high amino acid levels, and high amounts of ammonia in the blood. Everyone has some amino acids and ammonia in their blood, but high levels can be toxic.

These imbalances affect other enzymes that help break down amino acids and get rid of ammonia through the urine. In CIT-II, the enzyme arginosuccinate synthase no longer works correctly. This enzyme helps break down ammonia so the body can get rid of it through the urine. Without it, ammonia levels build up in the body.

CIT-II is an autosomal recessive genetic condition. This means that a child must inherit two copies of the non-working gene for CIT-II, one from each parent, in order to have the condition. The parents of a child with an autosomal recessive condition each carry one copy of the non-working gene, but they typically do not show signs and symptoms of the condition. While having a child with CIT-II is rare, when both parents are carriers, they can have more than one child with the condition. Learn more about autosomal recessive inheritance.

Support for Citrullinemia, Type II

Support Services

Support groups can help connect families who have a child or other family member affected with citrullinemia, type II 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 doctor to determine the next steps for your baby’s care. Your baby’s physician may help you coordinate care with a doctor who specializes in metabolism, a dietician who can help plan your child’s specialized diet, and other medical resources in your community. Depending on the symptoms your child experiences, your baby’s doctor may work with other doctors who specialize in treating the nervous system or the liver. Some children with citrullinemia, type II (CIT II) 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 CIT II 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 CIT II, 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

At this time we have not located a family story for this particular condition. If your family is affected by citrullinemia, type II and you would like to share your story, please contact us so other families may benefit from your experience.

References & Sources

Visit MedlinePlus Genetics for more condition information

Visit GeneReviews for more information on citrin deficiency

Read this fact sheet prepared by the Northwest Regional Newborn Screening Program for more information

Read this fact sheet prepared by the Iowa Department of Public Health for more information

ACT Sheets

Healthcare professionals can learn more about confirmatory testing by reading the American College of Medical Genetics and Genomics' Algorithm for Diagnosis and ACT Sheet, a guide for follow-up after newborn screening. You can visit this page of the ACMG website here.

Was this Helpful?

Your input helps us improve the site for parents and practitioners. Leave us feedback about this page.

Was this page helpful?

Was this Helpful? - Feedback

Your input helps us improve the site for parents and practitioners. Leave us feedback about this page.

We're sorry to hear that. How can we do to improve it?

This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.