Citrullinaemia (CIT)


Citrullinaemia (CIT) is an autosomal recessive disorder. Citrullinaemia (CIT) is caused by mutations in the ASS1 gene that is responsible for production of the argininosuccinate synthetase (ASS) enzyme. The symptoms of Citrullinaemia develop due to deficiency of this enzyme, which is needed to detoxify ammonia in the body. Failure to properly remove ammonia via synthesis of urea leads to the abnormal accumulation of ammonia in the blood (hyperammonemia).

Diagnosis of Citrullinaemia

The condition is diagnosed during newborn screening via the heel prick test taken 48-72 hours after birth. Diagnosis can also be made when symptoms present.


1:57,000 estimated worldwide.

Treatment for Citrullinaemia

The treatment of Citrullinaemia is aimed at preventing excessive ammonia from being formed or for removing excessive ammonia during a hyperammonemic episode. A low protein, high calorie diet supplemented by essential amino acids, multiple vitamins and calcium supplements may also be used. Dietary restrictions are aimed at limiting the amount of protein intake to avoid the development of excess ammonia. Prompt treatment is necessary when individuals have extremely high ammonia levels (severe hyperammonemic episode). Prompt treatment can avoid hyperammonemic coma and associated neurological symptoms. However, in some cases, especially those with complete enzyme deficiency, prompt treatment will not prevent recurrent episodes of hyperammonemia and the potential development of serious complications.

Support Links & Materials

Urea Cycle Disorders Handbook

UCD Fruit and Veg Counting Lists

UCD General Protein Counting Lists