In megaloblastic anemia, which of the following laboratory findings is characteristic of the bone marrow?

Question

Accepted Answer

A. Nuclear-cytoplasmic asynchrony with immature nucleus and mature cytoplasm. ## Bone Marrow Morphology in Megaloblastic Anemia

**Key Point:** The hallmark of megaloblastic erythropoiesis is **nuclear-cytoplasmic asynchrony** — the nucleus appears immature (open, fine chromatin pattern, prominent nucleoli) while the cytoplasm is mature and hemoglobinized.

### Morphologic Features of Megaloblasts

| Feature | Megaloblast | Normal Erythroblast |
|---------|-------------|--------------------|
| **Nucleus size** | Enlarged | Proportionate |
| **Chromatin pattern** | Fine, open, lacy | Coarse, condensed |
| **Nucleoli** | Prominent | Inconspicuous |
| **Cytoplasm** | Hemoglobinized (mature) | Immature, basophilic |
| **N:C ratio** | Increased | Normal |
| **Synchrony** | Asynchronous | Synchronous |

**High-Yield:** This asynchrony occurs because DNA synthesis is impaired while RNA and protein synthesis continue normally, causing the cytoplasm to mature faster than the nucleus.

### Additional Bone Marrow Findings

- **Hypercellularity** — increased cellularity due to compensatory erythroid hyperplasia
- **Increased mitotic activity** — many megaloblasts are dividing
- **Megaloblastic changes** — affect all cell lines (erythroid, myeloid, megakaryocytic)
- **Hypersegmented neutrophils** — mature neutrophils with ≥6 lobes (normal is 3–4)

**Clinical Pearl:** Hypersegmented neutrophils in the peripheral blood are a sensitive indicator of megaloblastic changes and can be seen even before anemia develops.

Answer

B. Increased myeloid-to-erythroid ratio

Answer

C. Absence of iron in erythroid precursors

Answer

D. Predominance of normoblasts with condensed chromatin

In megaloblastic anemia, which of the following laboratory findings is characteristic of the bone marrow?

Explanation

Bone Marrow Morphology in Megaloblastic Anemia

Morphologic Features of Megaloblasts

Additional Bone Marrow Findings

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Feature	Megaloblast	Normal Erythroblast
Nucleus size	Enlarged	Proportionate
Chromatin pattern	Fine, open, lacy	Coarse, condensed
Nucleoli	Prominent	Inconspicuous
Cytoplasm	Hemoglobinized (mature)	Immature, basophilic
N:C ratio	Increased	Normal
Synchrony	Asynchronous	Synchronous