Microcytic anemia: Pathology review

A 6-year-old boy is brought to the pediatrics PA by his parent, who states the patient has been lethargic for the past several weeks. The patient is in the 30th percentile for height and weight and has no significant past medical history. He has no abnormal bleeding, recent infections, or loss of sensation in the limbs. Temperature is 37.0°C (98.6°F), pulse is 96/min, respirations are 17/min, and blood pressure is 114/68 mmHg. Physical examination shows conjunctival pallor. Laboratory studies are as follows:  

Laboratory Value	Result	Reference Range
Hemoglobin	9.8 g/dL	13.5-17.5 g/dL
Mean corpuscular volume	78 fL	80-100 fL
Reticulocyte count	0.5%	0.5-1.5%
Serum iron	45 μg/dL	50-170 μg/dL
Ferritin	180 ng/mL	15-200 ng/mL
Lead	1 μg/dL (Normal < 5)	<5 μg/dL

   
Bone marrow aspirate with Prussian blue stain reveals ringed, immature red blood cells, as demonstrated below:

Image reproduced from Wikimedia Commons


 Treatment with which of the following is most likely to improve this patient’s condition?