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A 45-year-old man presented with pancytopenia due to myelodysplastic syndrome. The bone marrow showed marked trilineage dysplasia. Electron microscopy revealed that the majority of hematopoietic cells in the marrow had ultrastructural features of various stages of apoptosis ranging from margination and condensation of nuclear chromatin (arrowhead) to full nuclear pyknosis and vacuolization of the cytoplasm, with polarization of the organelles (arrow, x3700).
These findings suggest that in myelodysplasia, the proliferation of hematopoietic cells is outstripped by a simultaneous increase in the rate of apoptosis in the bone marrow.
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