Pernicious anaemia is an autoimmune gastritis that causes atrophy of all layers of both the body and fundus of the stomach, and loss of normal gastric glands, mucosal architecture, and parietal and chief cells, leading to atrophic gastritis. This atrophy reduces the number of parietal cells which secrete intrinsic factor (IF).
This is a companion discussion topic for the original article at https://patient.info/doctor/haematology/pernicious-anaemia-and-b12-deficiency