Citrullinemia type 1 is an inherited genetic disorder characterized by an accumulation of toxic substances including ammonia in the blood.
Affected individuals typically appear normal at birth, but as ammonia builds up in the bloodstream over time, they tend to experience a progressive lack of energy (lethargy), poor feeding, vomiting, seizures, and loss of consciousness. Some individuals may also develop serious liver problems, and the health problems associated with type 1 citrullinemia are life-threatening in many cases. The treatment of citrullinemia type 1 is aimed at preventing excessive ammonia from being formed, or for removing excessive ammonia during a hyperammonemia episode. Prompt treatment can avoid hyperammonemia coma, however, will not prevent recurrent episodes of hyperammonemia and the potential development of serious complications.
This condition is caused by pathogenic (disease-causing) variants in the ASS1 gene. Citrullinemia type 1 exhibits autosomal recessive inheritance, meaning both parents must be carriers to have a 25% chance of having a child with the condition. The risk of being a carrier is based on a person’s ancestry or ethnic background. Carriers do not typically show any signs or symptoms of the condition. Another name for this condition is citrullinuria.
Revised October 2022