megaloblast

blood cell

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June 30, 2026

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A megaloblast is a large, immature red blood cell that appears in the blood, particularly in cases of pernicious anemia. These abnormal cells are produced in the bone marrow as a result of impaired production of red blood cells, often due to a deficiency in vitamin B12 or folic acid. This deficiency hinders proper cell maturation, leading to ineffective red blood cell production. The mature red cells that do form are larger than normal, resulting in macrocytic anemia. While normoblasts are normal stages in red blood cell development, megaloblasts are considered abnormal, overlarge immature red cells.123

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blood disease
Megaloblastic anemias
…nucleated red cells known as megaloblasts, develops as the result of dietary deficiency of, faulty absorption of, or increased demands for vitamin B₁₂ or folic acid. When such a vitamin deficiency occurs, bone marrow activity is seriously impaired; marrow cells proliferate but do not mature properly, and erythropoiesis becomes largely…
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…nucleated red cells known as megaloblasts, develops as the result of dietary deficiency of, faulty absorption of, or increased demands for vitamin B₁₂ or folic acid. When such a vitamin deficiency occurs, bone marrow activity is seriously impaired; marrow cells proliferate but do not mature properly, and erythropoiesis becomes largely…
Read More

pernicious anemia
Pathophysiology
These cells, called megaloblasts, are for the most part destroyed in the bone marrow and are not released to the circulation. Some megaloblasts mature to become large red blood cells called macrocytes; they reach the circulation but function abnormally. A deficiency of white blood cells (leukopenia) and platelets…
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These cells, called megaloblasts, are for the most part destroyed in the bone marrow and are not released to the circulation. Some megaloblasts mature to become large red blood cells called macrocytes; they reach the circulation but function abnormally. A deficiency of white blood cells (leukopenia) and platelets…
Read More