A 50-year-old woman presents with easy fatigability, a smooth sore tongue, numbness and tingling of the feet, and weakness of the legs. A complete blood count shows a megaloblastic anemia that is not reversed by folate therapy. Hemoglobin is 5.6 g/dL, WBC count is 5,100/mL, and platelets are 240,000/mL. This patient most likely has a deficiency of which of the following vitamins?
High-Yield Explanation
Except for a few rare situations, vitamin B12 (cyanocobalamin) deficiency is usually a result of pernicious anemia, an autoimmune disease of the stomach. Vitamin B12 is required for DNA synthesis, and its deficiency results in large (megaloblastic) nuclei.Diagnosis: Vitamin B12 deficiency, pernicious anemia