Here, red cells are enlarged and slightly oval in shape with MCV 110 fL or more. The cell has a proportionate amount of hemoglobin, so MCHC is normal. A related finding is nuclear hypersegmentation of neutrophils. (A poly with 6 or more segments is virtually diagnostic.)Inadequate intake, absorption, impaired utilization, or increased need of B12 or folate leads to megaloblastic anemia. Replenishment rapidly resolves the abnormal morphology-new cells are normal. Megaloblastic changes are also seen in myelodysplastic syndromes. Here the changes are not affected by hematinic therapy.
One should measure:
Other conditions or medications can result in somewhat larger RBC, for example, alcohol ingestion, phenytoin, and reticulocytosis, eg, post hemorrhage; however, neutrophil segmentation is not usually affected in these conditions
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