All of the following are characteristic features of microcytic anemias EXCEPT:

Question

Accepted Answer

C. Increased serum ferritin in anemia of chronic disease. ## Microcytic Anemias: Characteristic Features

**Key Point:** Microcytic anemias are defined by MCV <80 fL and are primarily caused by iron deficiency, thalassemia, sideroblastic anemia, and anemia of chronic disease (ACD).

### Analysis of Each Option

| Feature | Iron Deficiency | Thalassemia Trait | ACD | Sideroblastic |
| --- | --- | --- | --- | --- |
| MCV | <80 fL | <80 fL | <80 fL | <80 fL |
| RDW | ↑ (high) | Normal | Normal | Normal |
| Reticulocyte count | Low | Normal/High | Low | Low |
| Serum ferritin | ↓ (low) | Normal | ↑ (high) | ↑ (high) |

**High-Yield:** In iron deficiency anemia, RDW is characteristically elevated because of the wide variation in red cell sizes (anisocytosis) as iron becomes depleted. This is one of the earliest laboratory changes.

**Clinical Pearl:** Anemia of chronic disease shows a paradoxical pattern — despite adequate iron stores (high ferritin), iron is sequestered in macrophages due to elevated hepcidin. This is why serum ferritin is elevated, not decreased.

### Why Option 3 Is Wrong

Increased serum ferritin is NOT a feature of microcytic anemias in general — it is specific to ACD and sideroblastic anemia. In iron deficiency anemia (the most common microcytic anemia), ferritin is **low**, not high. The stem asks for a feature true of microcytic anemias broadly, and ferritin elevation contradicts the iron deficiency pattern.

**Mnemonic:** **TAILS** — Thalassemia, ACD, Iron deficiency, Lead poisoning, Sideroblastic anemia (causes of microcytosis). Only ACD and sideroblastic have high ferritin.

Answer

A. Mean corpuscular volume (MCV) less than 80 fL

Answer

B. Increased red cell distribution width (RDW) in iron deficiency anemia

Answer

D. Normal or elevated reticulocyte count in thalassemia trait

All of the following are characteristic features of microcytic anemias EXCEPT:

Explanation

Microcytic Anemias: Characteristic Features

Analysis of Each Option

Why Option 3 Is Wrong

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Feature	Iron Deficiency	Thalassemia Trait	ACD	Sideroblastic
MCV	<80 fL	<80 fL	<80 fL	<80 fL
RDW	↑ (high)	Normal	Normal	Normal
Reticulocyte count	Low	Normal/High	Low	Low
Serum ferritin	↓ (low)	Normal	↑ (high)	↑ (high)