Citrullinemia Type I

Citrullinemia type 1 is an inherited disorder that causes ammonia and other toxic substances to accumulate in the blood. There are four types. The classic, most severe form, occurs in newborns, while a milder, later-onset form occurs in children or adults. There's also a form that occurs during or after pregnancy, and a form with no symptoms. In the classic form, symptoms occur right after birth and include excessive sleepiness, poor appetite, vomiting, and irritability. As ammonia builds up, muscle weakness, seizures, coma, and death can occur. Citrullinemia is caused by mutations in the ASS1 gene and is inherited in an autosomal recessive pattern.

This disorder is diagnosed through newborn screening and additional medical and genetic tests. Treatment includes removal of ammonia in the blood by medications and dialysis, as well as a lifelong low-protein diet. Liver transplantation is possible and, if done early in life, may eliminate the symptoms of the disorder. Left untreated, people with citrullinemia will build up very high levels of ammonia in the blood that can lead to brain damage and eventually death. Treated individuals can have normal growth and development.