Saturday, January 15, 2011

Megaloblastic Anemia (a)

Folic Acid Deficiency

Decreased intake
Inadequate diet—alcoholism, infancy

Impaired absorption
Malabsorption states
Intrinsic intestinal disease

Increased metabolism
Anticonvulsants, oral contraceptives

Increased loss


Increased requirement

Pregnancy, infancy, disseminated cancer, markedly increased hematopoiesis

Impaired use

Folic acid antagonists
Metabolic inhibitors of DNA synthesis and/or folate metabolism, e.g., methotrexate.

Folate metabolism:

the best sources of folate are fresh uncooked vegetables and fruits. Food folates are predominantly in polyglutamate form and must be split into monoglutamates

Phenytoin and a few other drugs inhibit folate absorption, while others, such as methotrexate, inhibit folate metabolism

The principal site of intestinal absorption is the upper third of the small intestine; thus, malabsorptive disorders that affect this level of the gut, such as celiac disease and tropical sprue, can impair folate uptake

conversion from dihydrofolate to tetrahydrofolate by the enzyme dihydrofolate reductase is particularly important.

Tetrahydrofolate acts as an acceptor and donor of one-carbon units in a variety of steps involved in the synthesis of purines and thymidylate, the building blocks of DNA, and its deficiency accounts for the inadequate DNA synthesis

measuring serum and red cell folate

symptoms referable to the alimentary tract are common and often severe. These include sore tongue and cheilosis.


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