Contributor: Gordon K. Klintworth
Megaloblastic anemia is a group of  anemias caused by an impaired DNA synthesis. Most cases result from a deficiency of cyanocobalamin [vitamin B12 deficiency] or from a deficiency of folic acid [folic acid deficiency]. Rarely megaloblastic anemia can result from a congenital or acquired synthesis of pyrimidines or purines. Cyanocobalamin deficiency may result from chronic gastritis (pernicious anemia). The anemia is a macrocytic anemia [anemia - macrocytic]. Megaloblastic anemia is also a feature of persons infected with Diphyllobothrium latum. Megaloblastic anemia may produce edema of the optic nerve head [edema - optic disc], retinal hemorrhages [hemorrhage - retina], and exudates.