Pernicious anemia occur due to
**Core Concept**
Pernicious anemia is a type of megaloblastic anemia caused by a deficiency of vitamin B12. It occurs due to impaired absorption of vitamin B12 in the gastrointestinal tract, leading to a decrease in the production of red blood cells.
**Why the Correct Answer is Right**
The primary reason for the deficiency of vitamin B12 in pernicious anemia is the autoimmune destruction of parietal cells in the stomach. Parietal cells are responsible for the production of intrinsic factor, a protein that binds to vitamin B12 in food and allows its absorption in the terminal ileum. Without intrinsic factor, vitamin B12 is not absorbed, leading to a deficiency. This deficiency impairs the production of red blood cells, leading to anemia. The impaired production of red blood cells is due to the inhibition of DNA synthesis, which is essential for cell division and growth.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the pathogenesis of pernicious anemia.
* **Option B:** While iron deficiency can cause anemia, it does not cause pernicious anemia specifically.
* **Option C:** Folate deficiency can also cause megaloblastic anemia, but it is not the cause of pernicious anemia.
**Clinical Pearl / High-Yield Fact**
Pernicious anemia is often associated with autoimmune disorders such as Hashimoto's thyroiditis and type 1 diabetes. It is essential to consider these conditions in patients with pernicious anemia.
**Correct Answer:** A. Autoimmune destruction of parietal cells in the stomach.