Megaloblast
As megaloblasts be unusually large, nuclear and hemoglobin-containing precursor cells of erythrocytes referred in the bone marrow. They develop from the still hemoglobin-free promegaloblast. The mature, enlarged erythrocytes are also called megalocytes .
The size of the cells is explained by the reduced DNA synthesis capacity , which delays cell division , while the production of RNA and cytoplasmic components is normal. This leads to an asynchrony between nucleus and cell maturation and thus to a relative increase in size.
Occurrence
The appearance of megaloblasts in the bone marrow smear is most often associated with folic acid deficiency anemia or vitamin B 12 deficiency anemia (pernicious anemia) . Both disease states are therefore also summarized under the term “ megaloblastic anemias ” (also referred to as “macrocytic anemias” due to the enlarged erythrocytes (macrocytes) that are usually also present).
They can also occur with myelodysplastic syndrome , erythroleukemia and after the use of cytostatics . Physiologically, they occur in the context of embryonic hematopoiesis ; more precisely, it is the blood cells that are formed in the first phase ( megaloblastic hematopoiesis ) in the yolk sac and stalk of the developing germ.
Individual evidence
- ^ Pschyrembel Clinical Dictionary . 261st edition. De Gruyter, Berlin 2007, ISBN 978-3110185348 .