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An abnormally large immature red blood cell (erythroblast) found especially in the blood of people with certain types of anemia and often associated with vitamin B12 deficiency.

meg′a·lo·blas′tic adj.


(Medicine) an abnormally large red blood cell precursor, present in certain types of anaemia
megaloblastic adj


(ˈmɛg ə ləˌblæst)

an abnormally large immature dysfunctional red blood cell found in the blood esp. of persons with pernicious anemia.
meg`a•lo•blas′tic, adj.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.megaloblast - abnormally large red blood cell present in pernicious anemia and folic acid deficiencymegaloblast - abnormally large red blood cell present in pernicious anemia and folic acid deficiency
erythrocyte, RBC, red blood cell - a mature blood cell that contains hemoglobin to carry oxygen to the bodily tissues; a biconcave disc that has no nucleus
References in periodicals archive ?
Megaloblastic anemia is an anemia that is characterized by the presence of precursor cells, megaloblast in the bone marrow and macrocytic red cells in the peripheral blood.4 These megaloblasts arise because of impaired DNA synthesis followed by ineffective erythropoiesis.4
Caption: FIGURE 5: Bone marrow smear showing multinucleated red cell (white arrow), typical megaloblast (arrowhead), and mitotic phase cell (yellow arrow).
Photomicrograph of Megaloblastic Anaemia; aspirate shows Megaloblasts with Sieve-Like Chromatin and Giant Metamyelocyte (Leishman Stain 1000x).
Uchino, "Proliferation of megaloblasts in pernicious anemia as observed from nucleic acid metabolism," Blood, vol.
Without the vitamin the red cells can become enlarged and will be immature and a strange shape (megaloblasts) and, as a consequence of this, they will be unable to marry with the oxygen-carrying Haemoglobin to deliver oxygen to wherever it is needed in the body--which is, incidentally, everywhere.