Lifelong Vitamin B12 supplementation. Vitamin B12 (cyanocobalamin) deficiency generally presents in patients as fatigue, diarrhea and headaches but can also be the cause of cognitive changes (difficulty concentrating, even mild dementia). Pernicious anemia is a macrocytic anemia, therefore laboratory findings indicate an increased mean corpuscular volume (MCV), with a decreased hemoglobin. A positive Schilling test indicates that the B12 deficiency is due to a lack of intrinsic factor. Lifelong cyanocobalamin supplementation (either orally or via injections) is needed to treat pernicious anemia. A is incorrect. Folic acid deficiency anemia is another common type of macrocytic anemia. However, cognitive deficits are not typically seen with folic acid deficiency. Furthermore, a schilling test would be negative and the methylmalonic acid (MMA) would be normal, rather than elevated. C is incorrect. Iron deficiency anemia causes a microcytic anemia, characterized by a decreased MCV. D is incorrect. A Coomb’s test is used to detect autoimmune hemolysis that may be suspected in patients with normocytic anemia (anemia with an MCV in the normal range). E is incorrect. Corticosteroids and iron supplementation are indicated as treatment in hemolytic anemia.