Journal #5584

You are urgently called to the newborn nursery to evaluate a 3-day-old term male infant who is lethargic. The baby was taking formula well for the first 2 days but vomited after his last 2 feedings and has become increasingly difficult to arouse. A review of the record reveals that he was born at 36 weeks ' gestation to a 30-year-old gravida 2, now para 2 woman. The mother is Rh-negative and received Rh immune globulin during the pregnancy. Pregnancy, labor, and delivery were uneventful; Apgar scores were 8 and 9 at 1 and 5 minutes. Family history is noncontributory. On physical examination, the baby appears well developed, is very jaundiced, and has hypotonia and tachypnea. He responds with a grimace to sternal rubbing but does not arouse to voice or to touch. Findings on abdominal examination are normal. You order a series of laboratory tests, start intravenous fluids, and arrange for transfer to the neonatal intensive care unit. A laboratory technician subsequently notifies you of some critical laboratory values, including a platelet count of 35x103/mcL (35x109/L), serum carbon dioxide of 4 mEq/L (4 mmol/L), anion gap of 28 mEq/L (28 mmol/L), serum ammonia of 250 mcmol/L, and total bilirubin of 20 mg/dL (342 mcmol/L). There are large ketones in the urine.
Of the following, the MOST likely diagnosis is:

bilirubin encephalopathy

citrullinemia

hypoxic-ischemic encephalopathy

propionic acidemia

transient hyperammonemia of the newborn