Citrullinemia, type II

Also known as:

• CIT II
• citrullinuria
• citrin deficiency
• CTLN II
• neonatal intrahepatic cholestasis caused by citrin deficiency (neonatal form only)
• NICCD (neonatal form only)
• citrullinemia

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.

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.