An elderly woman consults a physician because she is “feeling so tired all the time”. Intraoffice hematocrit is 35%. Peripheral blood smear shows many macrocytic red cells. On questioning, the woman, whose finances are limited, admits that has been living on a “tea and toast” type diet. She has been drinking a powdered orange juice substitute (Tang). She has not been taking vitamin pills because she feels she can’t afford them. A nutritional deficiency of which of the following is the most likely cause of this patient’s anemia?
C. Vitamin B12
D. Vitamin C
E. Vitamin K
The correct answer is A.
In real life, you would evaluate this woman for deficiencies in iron, folate, and Vitamin B12, since a woman with a diet this poor may very well have multiple problems. However, for the purpose of this type of test question, you should reason as follows: both vitamin B12 and folate deficiency can cause megaloblastic anemia. The patient’s “tea and toast” diet is much more suggestive of folate deficiency than B12 deficiency. Folate is widely found in plant and animal tissues, but is easily destroyed by over-cooking. Particularly vulnerable populations include the elderly, alcoholics, chronic liver disease patients, pregnant women, tropical sprue patients, chronic hemolytic anemia patients, and patients being treated (usually chronically) with certain medications (anti-convulsants, oral contraceptives, antimetabolites, and antibiotics that interrupt folate metabolism).
Iron deficiency (choice B) causes a microcytic anemia.
Vitamin B12 deficiency (choice C) is an important cause of megaloblastic anemia, but is more likely to be related to chronic gastritis with destruction of intrinsic factor-secreting parietal cells (pernicious anemia), fish tapeworm infestation, or malabsorption.
Vitamin C deficiency (choice D) is an occasional cause of megaloblastic anemia (often in conjunction with mild folate deficiency), but this patient is drinking a vitamin C-containing orange juice substitute.
Vitamin K deficiency (choice E) is usually related to either malabsorption or intestinal parasitic infection, and causes a bleeding tendency (because it is needed for synthesis of many clotting factors) rather than anemia.