Etiologies of Vitamin B12 Deficiency • Inadequate intake - Rare but seen in very strict vegans (no eggs or milk). • Abnormal gastric events - include being unable to dissociated vitamin B12 from food due to lack of stomach acid or enzymes. This is a recently recognized group of patients that may compose a very large subset of patients with vitamin B12 deficiency. 10-30% percent of patients with partial gastrectomy will develop vitamin B12 deficiency. The recent promiscuous use of H2 and proton pump blockers is leading to an increased incidence of patient's not absorbing vitamin B12. Finally, infection with H. pylori is also associated with decreased B12 absorption. • Deficient intrinsic factor - most commonly occurs due to destruction of parietal cells by autoantibodies (pernicious anemia). • Abnormal small bowel events - include pancreatic insufficiency, blind loops syndromes (bacterial absorbing vitamin B12-IF complexes) and patients infested with Diphyllobothrium latum. Metformin blocks B12 absorption at this step. • Abnormal mucosal events - including malabsorption syndromes and surgical removal of the terminal ileum. Dr. Thomas DeLoughery @Bloodman #B12 #VitaminB12 #deficiency #differential #diagnosis #hematology #nutrition
