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Indications And Usage Pernicious Anemia, Both Uncomplicated And Accompanied By Nervous System Involvement. Dietary Deficiency Of Vitamin B 12 , Occurring In Strict Vegetarians And In Their Breast-Fed Infants. (isolated Vitamin B 12 Deficiency Is Very Rare). Malabsorption Of Vitamin B 12 , Resulting From Structural Or Functional Damage To The Stomach, Where Intrinsic Factor Is Secreted Or To The Ileum, Where Intrinsic Factor Facilitates Vitamin B 12 Absorption. These Conditions Include Tropical Sprue, And Nontropical Sprue (idiopathic Steatorrhea, Gluten-Induced Enteropathy). Folate Deficiency In These Patients Is Usually More Severe Than Vitamin B 12 Deficiency. Inadequate Secretion Of Intrinsic Factor, Resulting From Lesions That Destroy The Gastric Mucosa (ingestion Of Corrosives, Extensive Neoplasia), And A Number Of Conditions Associated With A Variable Degree Of Gastric Atrophy (such As Multiple Sclerosis, Certain Endocrine Disorders, Iron Deficiency, And Subtotal Gastrectomy). Total Gastrectomy Always Produces Vitamin B 12 Deficiency. Structural Lesions Leading To Vitamin B 12 Deficiency Include Regional Ileitis, Ileal Resections, Malignancies, Etc. Competition For Vitamin B 12 By Intestinal Parasites Or Bacteria. The Fish Tapeworm (diphyllobothrium Latum) Absorbs Huge Quantities Of Vitamin B 12 And Infested Patients Often Have Associated Gastric Atrophy. The Blind-Loop Syndrome May Produce Deficiency Of Vitamin B 12 Or Folate. Inadequate Utilization Of Vitamin B 12 . This May Occur If Antimetabolites For The Vitamin Are Employed In The Treatment Of Neoplasia. For The Schilling Test.
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