Why is vitamin B12 anemia called megoblastic anemia?

Vitamin B12 anemia is called megaloblastic anemia because it is characterized by the presence of abnormally large red blood cells, known as megaloblasts, in the bone marrow. Megaloblasts are immature red blood cells that have not fully developed and are unable to function properly. They are larger in size compared to normal red blood cells and have an abnormal shape, often appearing oval or teardrop-shaped.

The development of megaloblastic anemia is primarily due to a deficiency of vitamin B12 or folate, which are essential nutrients involved in the synthesis of DNA and the maturation of red blood cells. When there is a deficiency of these nutrients, the production of DNA is impaired, leading to the formation of megaloblasts.

In the case of vitamin B12 deficiency, specifically, the lack of vitamin B12 affects the synthesis of a substance called myelin, which is a fatty material that surrounds and protects nerve cells. Without adequate myelin, the nerve cells in the bone marrow become damaged, resulting in the production of megaloblasts and the development of megaloblastic anemia.

Therefore, the term "megaloblastic anemia" refers to the presence of megaloblasts in the bone marrow and is associated with vitamin B12 or folate deficiency.