This is a megaloblastic bone marrow specimen obtained from a patient with pernicious anemia, taken at 500 x magnification. Even at this power you can see that many young NRBCs are present that look like wheels because of the deep-blue cytoplasm on the rim. The cytoplasm stains darker than the nucleus, which is typical for an early NRBC. Megaloblastic bone marrows in relapse also are distinguished by a maturation arrest in the erythroid series. In normal marrow, three fourths of the NRBCs are E5 and the remainder are E4 and younger. This is reversed in megaloblastic anemia.
Course Section: 05. Nucleated Red Blood Cells
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