CPS1 and Global developmental delay: For example, among two siblings with identical genotypes for CPS1D, one died as a neonate and the other received dietary therapy and functioned normally at age 45 years.16 Another child was rescued after fulminant neonatal‐onset but experienced severe global developmental delay.17 Three infants died despite treatment.12 In six infants with neonatal onset, one died and five exhibited developmental delay.18