Which anemia is noted for a lack of intrinsic factor that prevents B12 absorption?

The condition noted for a lack of intrinsic factor that prevents vitamin B12 absorption is pernicious anemia. Intrinsic factor is a glycoprotein produced by gastric parietal cells, and it is essential for the intestinal absorption of vitamin B12. Without intrinsic factor, vitamin B12 cannot be adequately absorbed in the terminal ileum, leading to a deficiency.

Pernicious anemia is specifically caused by an autoimmune destruction of these parietal cells, which results in both the absence of intrinsic factor and a resultant inability to absorb vitamin B12 effectively. This deficiency in vitamin B12 can lead to a range of issues including macrocytic anemia, neurological problems, and other systemic effects associated with B12 deficiency.

Other conditions listed, such as tropical sprue, transcobalamin deficiency, and blind loop syndrome, involve malabsorption or deficiencies but do not directly involve a lack of intrinsic factor specifically impacting B12 absorption in the manner characteristic of pernicious anemia. Thus, pernicious anemia is distinctly recognized for this mechanism of impaired vitamin B12 absorption.