A 35-year-old female is diagnosed with vitamin B12 deficiency anemia (pernicious anemia). The most likely cause is a decrease in:

a. ferritin.
b. gastric enzymes.
c. intrinsic factor.
d. erythropoietin.

ANS: C
The underlying alteration in pernicious anemia (PA) is the absence of intrinsic factor (IF), an en-zyme required for gastric absorption of dietary vitamin B12, a vitamin essential for nuclear matu-ration, and DNA synthesis in red blood cells. PA is not due to a decrease in ferritin, gastric en-zymes, or erythropoietin but to a lack of intrinsic factor.