B12 deficiency

• B12 and folate deficiency are identical hematologically and on blood smear.
• They both increase homocysteine levels, however only B12 is associated with an increased methylmalonic acid (MMA) level.
• MMA level is more sensitive; Clinically suspected B12 deficiency with equivocal B12 level? do MMA level to confirm.
• Pernicious anemia is the most common cause of vitamin B12 deficiency in whites of northern European background
• may have other associated autoimmune diseases, including autoimmune thyroid disease and vitiligo
• Pernicious anemia is confirmed with anti-intrinsic factor and anti-parietal cell antibodies.
• Red cells are destroyed as they leave the marrow, so the reticulocyte count is low.
• B12 and folate deficiency can cause pancytopenia as well as macrocytic anemia.
• It may cause erythroid hyperplasia and ineffective erythropoiesis in the bone marrow, which can result in markers of hemolytic anemia (eg, elevated LDH, low haptoglobin, indirect hyperbilirubinemia) and an absent reticulocyte response.
• Indirect hyperbilirubinemia can be seen due to ineffective erythropoiesis; 2/2 defective DNA synthesis with megaloblastic transformation of bone marrow and intramedullary hemolysis.
• Pancreatic enzymes are needed to absorb B12. They free it from carrier R-proteins and so it can bind with intrinsic factor. So, expect B12 deficiency in Pancreatic insufficiency.
• Neurological abnormalities will improve as long as they are minor (e.g peripheral) and of short duration.
• Beware of hypokalemia during replacement therapy (due to increase uptake for cell production by marrow)

Strong risk factors for Vit B12 Deficiency

• Age >65
• Gastric bypass surgery or Gastric Resection
• Terminal ileum disease (Crohn's disease )
• Metformin use