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Pathogenesis of megaloblastic anemia
Last reviewed: 23.04.2024
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Megaloblastic anemia unites a group of acquired and hereditary anemias, a common feature of which is the presence of megaloblasts in the bone marrow.
Regardless of the cause, hyperchromic anemia with characteristic changes in the morphology of erythrocytes, erythrocytes of oval form, large (up to 1 2 - 1 4 microns and more) is revealed in patients. There are erythrocytes with basophilic cytoplasmatic location, in many of them the remains of the nucleus are found (Jolly's bodies are the remains of nuclear chromatin, the Keboat rings are the remains of the nuclear envelope that look like a ringlet, Weidenreich dust particles are the remains of nuclear matter). The amount of reticulocytes decreased. Along with anemia, leukoneutro- and thrombocytopenia are possible, typically the appearance of polysigmented neutrophils.
In the bone marrow punctate the number of myelokaryocytes is increased, the erythroid germ is hyperplastic, the leukocyte-erythrocyte ratio is 1: 1, 1: 2 (3-4: 1 normally). Cells of the erythroid sprout are mainly represented by megaloblasts, which have larger dimensions than normal erythrocaryocytes, and a peculiar morphology of the nucleus. The core is eccentric, has a gently-mesh structure. There may be cells with degenerate-altered nuclei (in the form of ace club, mulberry, and others). Asynchronism of maturation of the nucleus and cytoplasm is noted; The cytoplasm is characterized by an earlier hemoglobinization, that is, a dissociation between the degree of maturity of the nucleus and the cytoplasm: a young nucleus and a relatively mature cytoplasm. The delay in ripening of granulocytes, the presence of giant metamyelocytes with a large nucleus and basophilic cytoplasm, stab and polysegmented neutrophils (with 6-10 segments) are detected. The number of megakaryocytes is normal or decreased; characteristic of the presence of giant forms of megakaryocytes, loosening of platelets is less pronounced.
Anemia in patients is due to ineffective erythropoiesis and shortening of the life span of red blood cells, which is confirmed by the increased content of erythrocaryocytes in the bone marrow with a reduced amount of reticulocytes in the peripheral blood. Typical is extramedullary hemolysis of erythrocytes - the life span of erythrocytes is reduced by 2-3 times in comparison with the norm, bilirubinemia. There are also ineffective granulocytopenia and thrombocytopoiesis. Thus, megaloblastic anemia is characterized by a change in all three germs of hematopoiesis.
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