Certified Neuroscience Registered Nurse (CNRN) Practice Exam

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In patients with pernicious anemia, what factor is typically lacking?

Intrinsic factor
Extrinsic factor
Hematopoietic factor
Platelet factor

The correct answer is: Intrinsic factor

Pernicious anemia is characterized by the inability to absorb vitamin B12 from the gastrointestinal tract, which is primarily due to a deficiency of intrinsic factor. Intrinsic factor is a glycoprotein produced by the parietal cells of the stomach, critical for the absorption of vitamin B12 in the ileum. Without sufficient intrinsic factor, vitamin B12 cannot bind properly, leading to impaired erythropoiesis and ultimately resulting in megaloblastic anemia. The lack of intrinsic factor often arises from an autoimmune destruction of the gastric parietal cells or an inherited condition, leading to symptoms associated with vitamin B12 deficiency, such as fatigue, weakness, and neurological changes. Understanding the role of intrinsic factor is essential in recognizing how its absence contributes to pernicious anemia.