Megaloblastic Anemia

Topics: Anemia, Pernicious anemia, Megaloblastic anemia Pages: 2 (483 words) Published: August 11, 2011
Megaloblastic anemias
Definition: groups of anemias characterized by macrocytosis (in the peripheral blood) and megaloblastic changes in the bone marrow. The megaloblasts are large blasts – bone marrow.
In periphery= macrocytosis= macrocytic anemia
Cause: IMPAIRED DNA SYNTHESIS due to folate/ B12 deficiency Vitamin B12 is involved in the synthesis of methionine from homocysteine;methionine is necessary for the synthesis of myeline; B12 deficiency will explain the neurological manifestation, because of demyelination. Also B12 is involved in the reaction that transforms folic acid from inactive form (methyl TH4) in the active form (TH4). Folic acid is involved in biosynthesis of nucleic acids (DNA) DNA synthesis impairment:

Affects tissues with rapid turnover: hematopoietic precursors, gastrointestinal epithelial cell Takes longer for nucleus to mature, but cytoplamic synthesis is not affected => Larger cells => megaloblastic haematopoiesis Megaloblastic changes in the bone marrow (BM):

On the erythroid line: abnormal precursors of erythrocytes called megaloblasts (large cells) On the granulocytic line: gigantic metamyelocytes
On the megacariocytic line: large megacariocytes, with polilobulated nucleus. Because of the destruction of the abnormal precursors in the BM (ineffective erythropoiesis, granulopoiesis, megacariopoiesis) on the hemogram we have macrocytic anemia/ leucopenia/trombocytopenia. On the peripheral blood smear: macrocytes, hypersegmented neutrophils. Source for both B12 and folate: exogenous.

Source: animal (meat, dairy products); usually dietary intake far exceeds needs => a deficiency is almost always due to malabsorbtion (exception: true vegetarians and their breast-fed infants). 1 μg is necessary every day.

Liver deposits last about 3-5 years.
Serum level: 200-600pg/ml.
Absorption takes place in the terminal ileonum and is dependant of intrinsic factor (IF, Castle’s) secreted by parietal cells of...
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