Pernicious anaemia is associated with the deficiency of:
**Core Concept**
Pernicious anemia is a condition characterized by the deficiency of **vitamin B12**, which is essential for the production of **red blood cells**. This deficiency is often caused by a lack of **intrinsic factor**, a protein in the stomach that is necessary for the absorption of vitamin B12.
**Why the Correct Answer is Right**
The correct answer is related to the role of **intrinsic factor** and **vitamin B12** in the body. **Vitamin B12** is crucial for the synthesis of **DNA** and the maintenance of the **nervous system**. A deficiency in **vitamin B12** can lead to **megaloblastic anemia**, a condition marked by the production of abnormally large red blood cells.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while **iron** is essential for the production of **hemoglobin**, its deficiency is associated with a different type of anemia.
**Option B:** This option is incorrect because **folate** deficiency can also cause **megaloblastic anemia**, but it is not the primary deficiency associated with pernicious anemia.
**Option C:** This option is incorrect because **vitamin B6** is not directly related to the pathophysiology of pernicious anemia.
**Clinical Pearl / High-Yield Fact**
Pernicious anemia is often associated with **autoimmune disorders**, such as **type 1 diabetes** and **thyroiditis**, and can also be caused by **gastric surgery** or **infections** that affect the stomach lining.
**Correct Answer:** D. Vitamin B12.