83. A 6-month-old male infant who is limp and exhibiting obtundation in the morning is brought to the emergency department. Bedside blood analysis reveals a significant metabolic acidosis, including an elevated lactate level and a capillary blood glucose level of 35 mg/dL (1.9 mmol/L and 3+ ketones in the urine. His newborn screening results were normal. His parents report that he only recently has been able to sleep through the night without waking for a feeding and that he has had a few episodes of morning lethargy that improved after his first morning feeding. The infant appears small and nearly comatose. He has chubby cheeks, a short nose, and a relatively small chin. He has a temperature of 37.8C, a heart rate of 155 beats/min, a respiratory rate of 15 breaths/min, and a blood pressure of 75/45 mm Hg. Cardiac examination reveals no murmur and a normal S1 and S2. The liver edge is palpable 3 cm below the right costal margin. The remainder of the physical examination findings are unremarkable. Of the following, the MOST likely diagnosis is a. fatty acid oxidation disorder b. glycogen storage disorder c. mitochondrial disorder d. organic acid disorder