Carbamoylphosphate Synthetase I Deficiency (CPS1)

Carbamoylphosphate synthetase I deficiency is an autosomal recessive disorder caused by pathogenic variants in the gene CPS1. It is a pan-ethnic disease with higher prevalence among Caucasians. Affected individuals develop high levels of ammonia in the bloodstream, which may be fatal or may result in permanent brain damage. Symptoms will present within the first few days of life and include sleepiness, poorly regulated breathing or body temperature, unwillingness to feed, vomiting, unusual body movements, and seizures. Developmental delay and intellectual disability are also associated with this disorder. Those affected with carbamoylphosphate synthetase I deficiency will always be at risk for hyperammonemia and will require constant surveillance. Some individuals will develop a later-onset form of the disease, but are still at risk for life-threatening bouts of hyperammonemia. The severity of the disease cannot be predicted based on the inherited variants.

For information about carrier frequency and residual risk, please see the residual risk table.