Q. A 3-day-old male infant is brought to the neonatal intensive care unit due to lethargy, poor feeding, and rapid breathing. The baby was born at full term without any complications. He seemed healthy at birth, but his condition began to deteriorate rapidly. His mother reports that she noticed him becoming increasingly less responsive. On examination, he has a decreased level of consciousness, and his breathing is labored. Newborn screening results show low levels of citrulline and arginine, but high levels of glutamine. Blood tests reveal severe hyperammonemia. Considering the history, clinical features, and laboratory findings, which of the following is the most likely diagnosis in this infant?