Citrullinemia type II

Other Names: Citrullinemia type 2; Adult-onset citrullinemia type 2; CTLN2; Citrin deficiency; Adult-onset citrullinemia type II; Adult-onset citrin deficiency; Adult-onset type II citrullinemia

Adult-onset citrullinemia type II is an inherited disorder that causes ammonia and other toxic substances to accumulate in the blood. The condition chiefly affects the nervous system, causing confusion, restlessness, memory loss, abnormal behaviors (such as aggression, irritability, and hyperactivity),seizures , and coma.

Risk factors

The features of adult-onset type II citrullinemia may also develop in people who as infants had a liver disorder called neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD). In many cases, the signs and symptoms of NICCD resolve within a year. Years or even decades later, however, some of these people develop the characteristic features of adult-onset type II citrullinemia. Type II citrullinemia may also develop in people who had a liver disorder called neonatal cholestasis during infancy.

Genetics

Autosomal recessive inheritance, a 25% chance

Adult-onset citrullinemia type II is caused by mutations in the ''SLC25A13'' gene . This condition is inherited in an autosomal recessive pattern. This gene makes a protein called citrin, which normally shuttles certain molecules in and out of mitochondria. These molecules are essential for the urea cycle and are also involved in making proteins and nucleotides. Mutations in SLC25A13 typically prevent the production of any functional citrin, which inhibits the urea cycle and disrupts the production of proteins and nucleotides. The resulting buildup of ammonia and other toxic substances leads to the symptoms of type II citrullinemia. Researchers have found many infants with neonatal intrahepatic cholestasis have the same mutations in the SLC25A13 gene as adults with type II citrullinemia.

signs and symptoms

Adult-onset citrullinemia type II chiefly affects the nervous system, causing neuropsychiatric symptoms including nocturnal delirium, aggression, irritability, hyperactivity, delusions, disorientation, restlessness, drowsiness, loss of memory, flapping tremor, convulsive seizures , and coma.

These signs and symptoms can be life-threatening. The signs and symptoms of this disorder appear suddenly during adulthood, usually between ages 20 and 50 years. The symptoms appear to be triggered by certain medications, infections, surgery, and alcohol intake.

Many individuals with adult-onset citrullinemia type II are fond of -rich and/or fatty foods and have an aversion to carbohydrate-rich foods. Pathologic findings include fatty infiltration and mild fibrosis of the liver despite little or no liver dysfunction.

Diagnosis

GeneReview articles describe the application of genetic testing to the diagnosis, management, and genetic counseling of patients with specific inherited conditions.

Treatment

There are multiple treatment methods. Low protein diets, are intended to minimize production of ammonia. Arginine, sodium benzoate and sodium phenylacetate help to remove ammonia from the blood. Dialysis may be used to remove ammonia from the blood when it reaches critical levels. In some cases, liver transplant has been successful. Individuals with adult-onset citrullinemia type II are encouraged to consume a diet rich in lipids and protein and low in carbohydrates. This may help to prevent hyperammonemia.

FDA-Approved Treatments

The medication(s) listed below have been approved by the Food and Drug Administration (FDA) as orphan products for treatment of this condition. Glycerol phenylbutyrate (Brand name: Ravicti)Use as a nitrogen-binding adjunctive therapy for chronic management of adult and pediatric patients at least 2 months of age with urea cycle disorders (UCDs) that cannot be managed by dietary protein restriction and/or amino acid supplementation alone. RAVICTI must be used with dietary protein restriction and, in some cases, dietary supplements (eg, essential amino acids, arginine, citrulline, protein-free calorie supplements).

Prognosis

The prognosis  for individuals with adult-onset citrullinemia type ll varies. In babies, the signs and symptoms usually resolve on their own. In adults, treatment may reduce the signs and symptoms of the condition. As adult-onset citrullinemia type ll can cause severe liver problems, untreated adults may need a liver transplant.

NIH genetic and rare disease info

• NIH info on Citrullinemia type II

Citrullinemia type II is a rare disease.