Which condition is associated with a deficiency of vitamin B12?

Pernicious anemia is specifically linked to a deficiency of vitamin B12 due to the body's inability to absorb the vitamin through the digestive tract. This condition arises from a lack of intrinsic factor, a protein produced by the stomach that is essential for the absorption of vitamin B12 in the intestines. Without adequate vitamin B12, the body cannot produce enough healthy red blood cells, leading to anemia.

Vitamin B12 is crucial for DNA synthesis and the proper formation of red blood cells. When it is deficient, it results in megaloblastic anemia, where red blood cells are larger than normal due to impaired maturation. While megaloblastic anemia is indeed related to vitamin B12 deficiency and is closely associated with pernicious anemia, pernicious anemia specifically identifies the mechanism behind the deficiency.

Iron deficiency anemia and folic acid deficiency are related to different causes; iron deficiency relates to insufficient iron for hemoglobin production, and folic acid deficiency pertains to the lack of folate, leading to similar but distinguishable anemia types. Therefore, pernicious anemia is the primary condition you would associate with a deficiency of vitamin B12.