megaloblast
Introduction
A distinct, nucleated erythroid cell characterized by a large size & an abnormal open nuclear chromatin pattern. These cells are not found in normal marrow, but are characteristically present in bone marrow & occasionally peripheral blood of patients pernicious anemia or other megaloblastic anemias. The term megaloblast has also been used to denote the earliest precursor of normal erythrocytes.
Because of the impaired ability to synthesize DNA, the cell cycle is prolonged. This is prolonged cell cycle results in enlarged cells, with nuclear maturation lagging behind cytoplasmic maturation. The nuclear chromatin pattern is moredelicate & more open. Karyorrhexis & Howell-Jolly bodies are frequently noted.
Megaloblastic development parallels normoblast maturation. Stages of maturation include promegaloblast, basophilic megaloblast, polychromatophilic megaloblast & orthochromatic megaloblast.
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References
- ↑ Clinical Diagnosis & Management by Laboratory Methods, 19th edition, J.B. Henry (ed), W.B. Saunders Co., Philadelphia, PA. 1996, pg 581, 599