A woman brings her 5-year-old son in for evaluation.

A woman brings her 5-year-old son in for evaluation. He has had progressive difficulty walking in the past few months and has seemed irritable. He has also seemed quite tired. He has vomited on one or two occasions. His past medical history is unremarkable. He was born after an uncomplicated, full-term pregnancy. He has had all of his vaccines and had achieved all of his developmental milestones for his age. He lives with his parents in a home that was built in the 1920s, which they have been renovating. On examination, he is somewhat restless but cooperative. His conjunctiva and mucous membranes are pale. Neurologic examination is significant for an ataxic gait (clumsiness). His general examination is otherwise unremarkable. A complete blood count (CBC) shows him to be anemic. A serum lead level is markedly elevated. You admit him to the hospital and start him on succimer. ◆ How does chronic lead exposure cause anemia? ◆ What is the mechanism of action of succimer