All of the following statements about macrocytic anemias are true EXCEPT:

Question

Accepted Answer

D. Reticulocytosis causes macrocytosis and is classified as a megaloblastic anemia. ## Macrocytic Anemias: Megaloblastic vs. Non-Megaloblastic **Key Point:** Macrocytic anemias are divided into two categories: **megaloblastic** (abnormal nuclear maturation) and **non-megaloblastic** (normal nuclear maturation). ### Classification of Macrocytic Anemias ```mermaid flowchart TD A[Macrocytic Anemia
MCV > 100 fL] --> B{Megaloblastic?} B -->|Yes| C[B12 deficiency
Folate deficiency
Drug-induced] B -->|No| D[Reticulocytosis
Hemolysis
Liver disease
Hypothyroidism
Alcohol abuse] C --> E[Nuclear-cytoplasmic
asynchrony] D --> F[Normal nuclear
maturation] ``` **High-Yield:** Reticulocytosis causes macrocytosis because reticulocytes are larger than mature RBCs (they contain residual RNA). However, reticulocytosis is **non-megaloblastic** — nuclear maturation is normal. ### Megaloblastic vs. Non-Megaloblastic Features | Feature | Megaloblastic | Non-Megaloblastic | | --- | --- | --- | | Nuclear-cytoplasmic asynchrony | Present | Absent | | Cause | B12/folate deficiency, drugs | Reticulocytosis, hemolysis, liver disease | | Hypersegmented neutrophils | Yes | No | | Bone marrow | Giant metamyelocytes, abnormal mitosis | Normal maturation | | MCV elevation | Marked (>100 fL) | Mild to moderate | **Clinical Pearl:** Hypersegmented neutrophils (>5 lobes) are a hallmark of megaloblastic anemia and occur in both B12 and folate deficiency due to impaired DNA synthesis affecting all dividing cells. ### Why Option 3 Is Wrong Reticulocytosis causes macrocytosis but is **NOT megaloblastic**. Reticulocytes are larger because they contain residual RNA and ribosomes, not because of abnormal nuclear maturation. This is a critical distinction in anemia classification.

Answer

A. Megaloblastic anemias are characterized by nuclear-cytoplasmic asynchrony

Answer

B. Folate deficiency results in hypersegmented neutrophils on peripheral blood smear

Answer

C. Vitamin B12 deficiency causes impaired DNA synthesis leading to macrocytosis

All of the following statements about macrocytic anemias are true EXCEPT:

Explanation

Macrocytic Anemias: Megaloblastic vs. Non-Megaloblastic

Classification of Macrocytic Anemias

Megaloblastic vs. Non-Megaloblastic Features

Why Option 3 Is Wrong

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Feature	Megaloblastic	Non-Megaloblastic
Nuclear-cytoplasmic asynchrony	Present	Absent
Cause	B12/folate deficiency, drugs	Reticulocytosis, hemolysis, liver disease
Hypersegmented neutrophils	Yes	No
Bone marrow	Giant metamyelocytes, abnormal mitosis	Normal maturation
MCV elevation	Marked (>100 fL)	Mild to moderate