Review Question - QID 108983

A 5-year-old boy is brought to the emergency department by his parents after a month of fatigue, difficulty concentrating, and diffuse abdominal pain. The pain has been mild, does not radiate, and was not associated with eating. He denies any nausea, vomiting, or diarrhea. His parents recently noticed that he began to drag his feet while walking. He has no significant past medical or surgical history and does not take any medication. His family recently began renovations on their home 3 months ago. On physical exam, his vital signs are within normal limits. Blood work shows the following findings:

Hematocrit: 30%
Total iron: 60 µg/dL
Ferritin: 215 ng/mL
Mean corpuscular volume: 65 µm^3

A peripheral blood smear shown in Figure A. Which of the following diseases involves the same metabolic pathway as the most likely diagnosis for this patient?