A 9-month-old exclusively breastfed infant who receives no complementary feeds presents with lethargy. Hb is 6.8 g/dL, MCV 62 fL, RDW 24%. Peripheral smear shows microcytic hypochromic cells with pencil cells. Which finding would be expected?

• A Elevated serum ferritin
• B Increased free erythrocyte protoporphyrin ✓
• C Normal total iron binding capacity
• D Low soluble transferrin receptor

Explanation

Iron deficiency in late infancy commonly follows inadequate dietary iron, since exclusive breastfeeding beyond 6 months provides insufficient iron. With depleted stores, iron incorporation into heme fails, so free erythrocyte protoporphyrin rises. Ferritin falls, TIBC rises, and soluble transferrin receptor increases reflecting expanded erythropoietic drive with limited iron supply. Thalassemia trait is excluded by the high RDW, since thalassemia characteristically shows a normal or low RDW with normal iron studies.

Reference: Nelson Textbook of Pediatrics, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.