In a patient presenting to the emergency department with fever, cough, leukocytosis with neutrophilia, microcytic anemia (hemoglobin 9 g/dL, mean corpuscular volume 65 fL), low serum iron, high ferritin, and elevated total iron‑binding capacity, what is the most likely type of anemia?

Iron Deficiency Anemia (Answer: A)

This patient has iron deficiency anemia (IDA), not anemia of chronic disease, despite the presence of acute infection. The laboratory pattern—particularly the elevated TIBC (430) combined with low iron (10) and microcytic anemia (MCV 65)—is diagnostic of iron deficiency, even though the ferritin is elevated at 250 ng/mL due to concurrent inflammation 1, 2.

Key Diagnostic Reasoning

Why Iron Deficiency Anemia:

The elevated TIBC (430) is the critical distinguishing feature here. In iron deficiency, the body attempts to compensate by increasing transferrin production, which raises TIBC. This patient's TIBC is markedly elevated, which is incompatible with anemia of chronic disease 3.

The iron studies pattern clearly indicates IDA:

• Low serum iron (10 μg/dL)
• High TIBC (430 μg/dL) - this is the key discriminator
• Transferrin saturation would be <15% (calculated as 10/430 = 2.3%)
• Severe microcytosis (MCV 65 fL)

Why NOT Anemia of Chronic Disease:

While the patient has acute infection (fever, cough, leukocytosis) and elevated ferritin, anemia of chronic disease is characterized by LOW or normal TIBC, not elevated TIBC 1, 2. In ACD:

• Iron is trapped in macrophages due to hepcidin upregulation
• TIBC is typically <250 μg/dL 4
• Transferrin saturation <16% with ferritin >100 μg/L 1

Interpreting Ferritin in Inflammation:

The ferritin of 250 ng/mL appears elevated but does not exclude iron deficiency in the setting of acute inflammation. Guidelines clearly state that in the presence of inflammation, ferritin levels up to 100 μg/L may still indicate iron deficiency, and even levels between 30-100 μg/L suggest combined deficiency 1, 2. The ferritin is acting as an acute-phase reactant here, masking the underlying iron deficiency 5, 6.

Why NOT the Other Options:

• Hemolytic anemia (C): Would show elevated LDH (this patient's LDH is normal at 200), elevated reticulocytes, elevated indirect bilirubin, and low haptoglobin—none of which are present 3

• Thalassemia (D): While microcytic, thalassemia typically shows MCV reduced out of proportion to anemia severity, normal or elevated RBC count, and normal iron studies with normal TIBC. The elevated TIBC here excludes thalassemia 5, 7

• Sideroblastic anemia (E): Would show elevated or normal ferritin with elevated iron and normal or low TIBC, plus ring sideroblasts on bone marrow examination 3

Clinical Algorithm for Microcytic Anemia with Inflammation:

1. Check TIBC first when ferritin is equivocal (30-500 ng/mL) in inflammatory states

   • TIBC >350 μg/dL → Iron deficiency
   • TIBC <250 μg/dL → Anemia of chronic disease
   • TIBC 250-350 μg/dL → Mixed picture

2. Calculate transferrin saturation (iron/TIBC × 100)

   • <15% with high TIBC → Iron deficiency 3
   • <16% with low TIBC and ferritin >100 → ACD 1

3. Assess MCV severity

   • MCV <75 fL has 83% positive predictive value for iron deficiency 4
   • MCV ≥86 fL essentially excludes iron deficiency 4

Common Pitfall to Avoid:

Do not be misled by elevated ferritin in the setting of acute infection. Ferritin is an acute-phase reactant and can be falsely elevated during inflammation, infection, or malignancy 5, 6. The TIBC remains the most reliable discriminator between IDA and ACD when inflammation is present 4, 7. This patient's TIBC of 430 definitively indicates iron deficiency despite the ferritin of 250.