Anaemia due to deficiency of B_{12} Vitamin (Cynocobalamine) is known as :

Question

Accepted Answer

Pernicious anaemia is the correct answer for anaemia due to deficiency of Vitamin B_{12} (Cyanocobalamin). Here is a detailed explanation:

1. **Explanation for Option 2 (Pernicious anaemia):**
   - Pernicious anaemia is a specific type of megaloblastic anaemia that occurs due to the deficiency of Vitamin B_{12}. This deficiency is often caused by the body's inability to absorb Vitamin B_{12 from the gastrointestinal tract, which is typically due to a lack of intrinsic factor, a protein necessary for Vitamin B_{12} absorption. Pernicious anaemia is characterized by the production of large, immature, and dysfunctional red blood cells (megaloblasts) in the bone marrow and their presence in the bloodstream. The term "pernicious" historically refers to the condition being potentially deadly if untreated, due to its severe impact on the body's ability to produce healthy red blood cells.

2. **Explanation for why other options are incorrect:**

- **Option 1 (Microcytic anaemia):**
     - Microcytic anaemia is characterized by smaller than normal red blood cells and is typically associated with iron deficiency or conditions like thalassemia. It is not related to Vitamin B_{12} deficiency, which causes larger red blood cells, not smaller ones.

- **Option 3 (Megaloblastic anaemia):**
     - While megaloblastic anaemia is indeed associated with Vitamin B_{12} deficiency, it is a broader category that includes anaemia caused by folate deficiency as well. Pernicious anaemia is a specific type of megaloblastic anaemia caused by Vitamin B_{12} deficiency due to intrinsic factor deficiency. Therefore, while related, the term "pernicious anaemia" is more specific to the context of Vitamin B_{12} deficiency due to absorption issues.

- **Option 4 (Microcytic hypochromic anaemia):**
     - This type of anaemia is characterized by red blood cells that are both smaller than normal (microcytic) and paler than normal (hypochromic), typically due to iron deficiency. It is not related to Vitamin B_{12} deficiency, which causes macrocytic (large cell) anaemia.

In conclusion, Option 2, Pernicious anaemia, is the correct answer as it specifically refers to the type of anaemia caused by Vitamin B_{12} deficiency due to absorption issues, distinguishing it from other types of anaemia that have different causes and characteristics.