Regarding the pathophysiology and laboratory diagnosis of iron deficiency anemia, all of the following statements are correct EXCEPT:

Question

Accepted Answer

B. Peripheral blood smear shows target cells and pencil cells due to reduced hemoglobin content relative to cell volume. ## Pathophysiology and Diagnosis of Iron Deficiency Anemia

### Correct Answer Explanation

**Key Point:** Target cells (codocytes) are NOT a characteristic finding in iron deficiency anemia. Target cells are seen in conditions with **decreased hemoglobin-to-cell volume ratio** such as **liver disease, thalassemia trait, and post-splenectomy**—not IDA.

**High-Yield:** The peripheral smear in IDA shows:
- **Microcytes** (small RBCs)
- **Hypochromia** (pale central pallor, >1/3 of cell diameter)
- **Pencil cells** (elliptocytes, anisopoikilocytosis)
- **Occasional polychromasia** (reticulocytosis in response to anemia)

~~Target cells~~ are NOT seen in IDA; they indicate a different pathophysiology.

### Correct Statements Explained

| Statement | Truth | Rationale |
|-----------|-------|----------|
| **Iron & heme synthesis** | ✓ Correct | Iron is the central atom in protoporphyrin IX; without it, hemoglobin cannot be synthesized |
| **sTfR elevation** | ✓ Correct | sTfR ↑ in IDA and remains elevated despite inflammation; superior to ferritin for IDA diagnosis |
| **DMT1 absorption** | ✓ Correct | DMT1 (also called NRAMP2) is the primary transporter for Fe²⁺ in duodenum/proximal jejunum |

### Mnemonic for Target Cells
**"Target = Thin Hemoglobin Layer"** — Seen in liver disease, thalassemia trait, post-splenectomy (conditions with ↓ Hb relative to cell size). NOT in IDA.

Answer

A. Serum soluble transferrin receptor (sTfR) levels are elevated and remain high even in the presence of inflammation, making it superior to ferritin for diagnosis

Answer

C. Iron absorption occurs primarily in the duodenum and proximal jejunum via divalent metal transporter 1 (DMT1)

Answer

D. Microcytic hypochromic anemia develops because iron is essential for heme synthesis and hemoglobin production

Regarding the pathophysiology and laboratory diagnosis of iron deficiency anemia, all of the following statements are correct EXCEPT:

Explanation

Pathophysiology and Diagnosis of Iron Deficiency Anemia

Correct Answer Explanation

Correct Statements Explained

Mnemonic for Target Cells

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Statement	Truth	Rationale
Iron & heme synthesis	✓ Correct	Iron is the central atom in protoporphyrin IX; without it, hemoglobin cannot be synthesized
sTfR elevation	✓ Correct	sTfR ↑ in IDA and remains elevated despite inflammation; superior to ferritin for IDA diagnosis
DMT1 absorption	✓ Correct	DMT1 (also called NRAMP2) is the primary transporter for Fe²⁺ in duodenum/proximal jejunum