Iron deficiency and iron deficiency anemia (pediatrics) Quiz: Ace Your Exams

A 2-year-old boy presents to the pediatrician with his parents for a routine well-child visit. He is a picky eater and primarily eats white pasta and bread. Parents give him 30 oz/day of milk to make sure he is full. They report that he needs two naps per day despite sleeping for 12 hours at night. They are not currently giving him multivitamins. Temperature is 37.3°C (99°F), pulse is 145/min, respirations are 30/min, blood pressure is 90/58 mmHg, and oxygen saturation is 99% on room air. Length is at the 60^th percentile, weight is at the 82^nd percentile, and head circumference is at the 45^th percentile. On physical examination, he appears pale with cracks at the bilateral oral commissures. On cardiac exam, there is tachycardia with a soft 2/6 systolic murmur heard at the left sternal border. Lungs are clear to auscultation and there is no increased work of breathing. Nails appear brittle. Which of the following laboratory results is most consistent with the likely underlying diagnosis?