How does vitamin B12 deficiency lead to megaloblastic anemia?

Vitamin B12 deficiency leads to megaloblastic anemia because vitamin B12 is crucial for DNA synthesis and red blood cell formation. Without sufficient vitamin B12, red blood cells cannot mature properly, leading to the production of large, immature cells called megaloblasts. These megaloblasts are less effective at carrying oxygen, resulting in anemia.

Vitamin B12 deficiency leads to megaloblastic anemia through the following steps:

1. Impaired DNA synthesis: Vitamin B12 is essential for the production of tetrahydrofolate (THF), a critical cofactor in DNA synthesis.
2. Inhibited red blood cell production: Without sufficient THF, red blood cell production is impaired, leading to a decrease in the number of red blood cells.
3. Abnormal cell growth: Vitamin B12 deficiency disrupts normal cell growth and maturation, causing red blood cells to become larger and more immature (megaloblasts).
4. Inefficient hemoglobin synthesis: Megaloblasts have impaired hemoglobin synthesis, leading to reduced hemoglobin levels.
5. Anemia develops: The combination of decreased red blood cell count and reduced hemoglobin levels results in megaloblastic anemia.