Pernicious anemia happens when your immune system attacks stomach cells that make intrinsic factor, a protein needed to absorb vitamin B12. Gastrectomy, chronic gastritis, and strict vegan diets can also cause it by reducing B12 intake or absorption.
Pernicious MEA can be due to an autoimmune response which destroys the ability of the body to absorb vitamin B12. There's a glycoprotein called intrinsic factor that is released by the parietal cells in the stomach, and intrinsic factor's job is to allow the body to absorb vitamin B12. But with pernicious anemia, there is an autoimmune response in the body where the body either attacks those parietal cells before before they can produce the intrinsic factor, or it attacks the intrinsic factor itself. Either way, this interrupts the body's ability to absorb and utilize B12. Pernicious anemia can also be caused by a lack of vitamin B12 intake or absorption. This can be from chronic gastritis, a gastrectomy, or due to a lack of vitamin B12 intake. With diets such as a strict vegan or vegetarian diet.
