0521779407-07 CUNY1086/Karliner 0 521 77940 7 June 4, 2007 21:10
576 Folic Acid/Cobalamin (Vitamin B12) Deficiency➣Usurpation of luminal cobalamin
➣Inadequate/Diseased ileal absorptive surface
➣Inactivation of cobalamin by nitrous oxide
➣Common Causes
Vegetarians (dietary cobalamin deficiency may be most
common cause in developing countries). Note: Nonvege-
tarians who eat small portions of meat infrequently can
have low cobalamin intakes comparable to vegetarians/
vegans.
Atrophic/partial gastritis with hypochlorhydria, proton-pump
inhibitors
Total/partial gastrectomy, pernicious anemia (PA)
Pancreatic insufficiency, Zollinger-Ellison syndrome
Bacterial overgrowth syndromes (blind loops, diverticulosis,
strictures, fistulas, anastomoses, scleroderma, hypogamma-
globulinemia), fish-tapeworm
Ileal bypass/resection/fistula
Tropical/nontropical sprue, Crohn’s disease, TB-ileitis, amy-
loidosis
Drugs (slow-K, biguanides, cholestyramine, colchicine, neo-
mycin)
Nitrous oxide inhalation
Pernicious anemia (PA): most common cause of cobalamin defi-
ciency in the West; caused by autoimmune destruction of gastric
parietal cells leading to intrinsic factor (IF) deficiency. Undiag-
nosed PA in USA >60-years age group (∼1.5% men,∼4% African-
American/Caucasian women). Anti-IF antibodies are highly specific
for PA (60% of PA have anti-IF antibodies in serum). Positive family
history (in 30%). PA is associated with autoimmune diseases (i.e., the
polyglandular autoimmune syndrome, Graves’ disease, Hashimoto’s
thyroiditis, vitiligo, Addison’s disease, idiopathic hypoparathyroidism,
primary ovarian failure, myasthenia gravis, type I diabetes, and adult
hypogammaglobulinemia).
■Folate Deficiency – General Mechanisms
■(multiple causes in same patient)
➣Decreased intake/absorption
➣Increased requirement/destruction/excretion
➣Common Causes
Poverty, famine, institutionalized individuals (psychiatric/
nursing homes/chronic debilitating disease), ethnic cooking
techniques, dieting