A 82-year-old woman is brought to the hospital because of functional decline at home and an inability to care for herself. She has a prior history of hypertension and dyslipidemia, and her medications include hydrochlorothiazide and atorvastatin. She looks disheveled, pale, and has muscle wasting; her heart and lungs are clear and there are no focal neurologic findings. Her hemoglobin is 9 g/dL, MCV 105 fL,
WBC 4500/mL, and platelets 100,000/mL. The blood film shows macrocytic RBCs and hypersegmented
neutrophils. Which of the following vitamin deficiencies is most likely responsible for her pancytopenia?
(A) B12 (cyanocobalamin)
(B) The macrocytosis and hypersegmented neutrophils suggests a megaloblastic anemia due to either folate or vitamin B12 deficiency. Folate deficiency results from decreased intake and malabsorption. Body folate stores are meager (only 3 months on average, compared to a few years for vitamin B12), and therefore easily depleted when intake is poor. Alcohol itself can depress folate levels acutely, and also can cause pancytopenia directly