Repeated USMLE Questions- A Case of Macrocytic Anemia
Dr Ray Makar
Q- A 34-year-old woman presents with weakness, easy fatigability and numbness and tingling of her arms and legs. CBC reveals pancytopenia and marked increase in the MCV of erythrocytes. More investigations reveal chronic atrophic gastritis. What is the most likely diagnosis?
A- Aplastic anemia
B- Folic acid deficiency anemia
C- Iron deficiency anemia
D- Vitamin B12 deficiency
D- Vitamin B12 deficiency- This is a typical case of vitamin B12 deficiency macrocytic anemia due to lack of intrinsic factor results from gastric atrophy. Intrinsic factor is essential for Vitamin B12 abortion.
Q- Which one of the following conditions is NOT a common cause of vitamin B12 deficiency?
A- Diet deficiency of vitamin B12
B- Gastric bypass
C- Intrinsic factor deficiency
D- Malabsorption syndrome
A- Diet deficiency of vitamin B12- This deficiency is very rare although it is starting to be seen due to aggressive vegan diet but it is still not as common as other choices.
Q- Which of the following substances is elevated due to vitamin B12 deficiency?
A- Cyanocobalamin
B- Folic acid
C- Homocysteine
D- Hemosiderin
C- Homocysteine- It is elevated as well as methylmalonic acid due to deficiency of vitamin B12 which is involved in the conversion of homocysteine to methionine. Cyanocobalamin is a different name of vitamin B12 and folic acid deficiency leads to macrocytic anemia, not high levels. Hemosiderin is involved in hemochromatosis and some other medical conditions.