Megaloblastic Anemia

Related Cases: HP-257; HP-283

  • Mostly associated with vitamin B12 or folate deficiency due to inadequate uptake, excessive usage, absorption problem, GI surgery or medication;

  • Serum LDH often dramatically elevated;

  • Peripheral blood: Megaloblastic anemia with numerous ovalocytes, and often hypersegmented neutrophils. However, MCV may be within normal range in some cases;

  • Bone marrow:

    • Mostly hypercellular marrow with marked erythroid hyperplasia and left shifted granulopoiesis.

    • Erythroid precursors with megaloblastic changes: large regular nuclei and fine chromatin. Compared to cytoplasm, the nuclear maturation is delayed since both vitamin B12 and folate are important in DNA synthesis.

    • Occasional hypersegmented neutrophils and giant bands or metamyelocytes.

    • Subtle dysplastic changes may be present.

  • Differential diagnosis:

    • MDS with megaloblastoid changes: Megaloblastoid erythroid precursors typically show irregular nuclear contours, coarse and clumped chromatin, and more obvious dysplastic cytological features. The nuclei are often relative more mature than the cytoplasm.

    • AML: The hypercellular marrow with sheets of immature erythroid cells on the core biopsy may closely resemble AML. On the tissue sections, the early erythroid precursors are large in size and have high N/C ratio, and importantly, the nuclei are usually very round with clear chromatin and a central large nucleolus.

Reference

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Last updated: 05/10/2015