PRESENTATION: An 18-month-old girl presents to the hematology clinic for follow-up of severe anemia of unknown etiology. On presentation she is noted to be tachypneic and in respiratory distress. Her examination is significant for retractions, diminished breath sounds, crackles, and oxygen saturations of 91 to 93 on room air. Her medical history is significant for an admission to the PICU 3 months earlier when she presented with fevers, pallor, and respiratory distress. The initial evaluation at that time was significant for a hemoglobin level of 2.6 g/dL (26 g/L) (reference range, 10.5-13.5 g/dL 105-135 g/L) and findings on chest radiography (CXR) of multifocal pneumonia, particularly on the right side (Fig 1), for which she was treated with antibiotics. Results of a hemoglobin screening test at 9 months of age were normal, and there was no significant history of hematuria, hematemesis, hemoptysis, bloody stools, skin bruises, or excessive milk intake (24 oz daily). Evaluation showed mild microcytosis (mean corpuscular volume of 73.3 μm~3 73.3 fL) (reference range, 70-86 μm~3 70-86 fL), a low iron level (19 μg/dL 3.4 μmol/L) (reference range, 65-175 μg/dL 11.6-31.3 μmol/L), mildly elevated total iron-binding capacity (423 μg/dL 75.7 μmol/L) (reference range, 250-410 μg/dL 44.8-73.4μmol/L), transferrin saturation of 4 (reference range, 26-43), a normal transferrin level (338 mg/dL 41.57 μmol/L) (reference range, 200-360 mg/dL 24.6-44.28 μmol/L), and a normal ferritin level (47 ng/mL 47 μg/L) (reference range, 10-150 ng/mL 10-150 μg/ L). Based on the total iron-binding capacity, the transferrin saturation, and the finding of many red blood cells with enlarged central pallor on her peripheral blood smear, she was diagnosed as having iron deficiency anemia (IDA) and transfused with packed red blood cells. She was discharged on supplemental iron with evaluation ongoing because her iron studies did not fully explain her degree of anemia.
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