Carbamoylphosphate synthetase I (CPS1) deficiency is a member of the urea cycle disorders group, characterized by the absence of a crucial liver enzyme.
This deficiency results in elevated ammonia levels in the bloodstream (hyperammonemia), particularly hazardous to the brain. Typically, most affected individuals exhibit symptoms within the first few days of life, known as the neonatal-onset form. These symptoms may encompass unusual drowsiness, irregular breathing or body temperature regulation, feeding reluctance, post-feeding vomiting, abnormal movements, seizures, or even comatose states. Surviving infants may encounter symptom relapses if their diet isn’t meticulously managed or if they face infections or other stressors, often accompanied by developmental delays and intellectual impairment. In rarer instances, CPS1 deficiency presents later in childhood or adulthood as the late-onset form, albeit some individuals may still confront hyperammonemic coma and life-threatening complications despite milder symptoms.
CPS1 is caused by pathogenic (disease-causing) variants in the CPS1 gene and exhibits autosomal recessive inheritance. This means that both parents must be carriers to have a 25% chance to have a child with the condition. The risk of being a carrier is based on a person’s ancestry or ethnic background.
Other names for this condition is congenital hyperammonemia, type I.
Resources:
National Organization for Rare Disorders
Revised September 2023
