The result of this nuclear-cytoplasmic dissociation is production of cells that are larger than normal due to the defective DNA and RNA synthesis. Megaloblastic changes affect all dividing cells, (e.g. blood, intestine, skin) and the hematopoietic effects involve all blood cell lines.
Megaloblastic anemias can be classified into two major categories based on etiology. The major divisions are vitamin B12 (cobalamin) deficiency and folic acid deficiency. Vitamin B12 and folic acid are both essential for the synthesis of DNA and RNA.
One of the major causes of vitamin B12 deficiency is pernicious anemia, and autoimmune condition that is characterized by the inability of the gastric mucosa to produce intrinsic factor (IF). Intrinsic factor is necessary of the transportation of vitamin B12 across the intestinal mucosa.
In severe megaloblastic anemia, many developing red blood cells are destroyed in the bone marrow before they are released into the circulation.
Megaloblastic anemia
