Snap Shot A 59-year-old woman has the gradual onset of emotional lability, forgetfulness, and difficulty organizing her finances. PE reveals a bilateral Babinski sign. Deficiency Causes pernicious anemia intrinsic factor required for absorption in the terminal ileum B12 not absorbed when intrinsic factor not produced from the parietal cells of the stomach gastric bypass surgery less intrinsic factor produced resection of terminal ileum e.g. Crohn's disease malabsorption sprue, enteritis, Diphyllobothrium latum bacterial overgrowth of terminal ileum vegan diets Presentation neurologic findings are unique to B12 deficiency numbness and parastesias of the extremities hyporeflexia vibratory loss ataxia demetia neurological deficits can occur even if hematology in normal Evaluation serum B12 increased methylmalonic acid and homocysteine levels pancytopenia Schillings Test smear shows hypersegmented neutrophils, macroovalcytes since B12 folate is needed in DNA synthesis, absence results in large immature nuclei in all nucleated cells in the marrow. Most of these abnormal cells are destroyed and therefore the patients present with pancytopenia