Review Question - QID 215162

A 6-year-old boy is brought to clinic to establish care. He and his family recently immigrated from Nigeria 2 weeks ago. The patient has a history of frequent hospitalizations back in Nigeria. The patient currently takes no medications. He is up to date on his vaccinations. His temperature is 99.8°F (37.7°C), blood pressure is 105/72 mmHg, pulse is 76/min, and respirations are 12/min. The patient’s height and weight are both in the 10th percentile. Physical exam reveals a thin, well-appearing boy with conjunctival pallor. His abdomen is non-tender and there is no hepatosplenomegaly. Initial laboratory testing reveals some abnormalities prompting the pediatrician to order a peripheral blood smear, which is shown in Figure A. Which of the following is the most likely cause of the finding seen on the blood smear?