Megaloblastic anemia

Megaloblastic anemia is a blood disorder caused by impaired DNA synthesis, producing abnormally large red-cell precursors in bone marrow and often enlarged red blood cells.

Vitamin B12 deficiency: A shortage of cobalamin that disrupts blood formation and nervous-system function. It impairs DNA synthesis and is a major cause of megaloblastic anemia.
Pernicious anemia: An autoimmune disorder that prevents adequate vitamin B12 absorption by disrupting intrinsic factor or its production. It is a common cause of vitamin B12 deficiency and consequent megaloblastic anemia.
Complete blood count: A blood test measuring red cells, white cells, platelets, hemoglobin, and related indices. Its cell counts and red-cell indices can reveal anemia and macrocytosis.
Non-megaloblastic macrocytic anemia: Macrocytic anemia in which red cells enlarge without the characteristic marrow changes of impaired DNA synthesis. It can raise mean corpuscular volume without producing megaloblastic morphology.
Folate deficiency: Insufficient folate, a B vitamin needed to make nucleotides and support cell division. It limits DNA synthesis in rapidly dividing marrow cells.
Intrinsic factor: A stomach-produced protein required for absorption of vitamin B12 in the terminal ileum. Loss of intrinsic factor can cause the B12 deficiency underlying megaloblastic anemia.
Mean corpuscular volume: A measure of the average volume of red blood cells. An elevated value is a common clue, though it does not identify the cause.
Iron-deficiency anemia: Anemia caused by insufficient iron for hemoglobin production, usually producing small red blood cells. Its typically microcytic cells contrast with the enlarged cells of megaloblastic anemia.
Ineffective erythropoiesis: Failure of developing red blood cells to mature successfully, despite active production in bone marrow. Megaloblastic precursors often die in marrow before becoming circulating red cells.
Celiac disease: An immune-mediated small-intestinal disease triggered by gluten that damages the intestinal lining. Intestinal injury can reduce folate absorption and contribute to megaloblastic anemia.

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