Review Question - QID 214361

A 2-month-old boy is brought to the emergency department with poor feeding and lethargy. The patient was born to a 26-year-old mother at 37 weeks gestation via a spontaneous vaginal delivery. There were no obstetric complications. The parents deny any fever, cough, foul-smelling urine, nausea, or vomiting. Physical examination is notable for conjunctival pallor and hypertelorism. Laboratory studies are shown:

Hemoglobin: 5 g/dL
Platelet count:  250,000/mm^3
Mean corpuscular volume: 105 µm^3
Leukocyte count: 6,000/mm^3 with normal differential
Reticulocyte count: 0.2 %
Erythrocyte adenosine deaminase activity: Increased
Hemoglobin F: Increased

Which of the following is most likely the diagnosis?