Autoimmune Gastritis

Autoimmune gastritis is a chronic immune-mediated disease in which the body's immune response targets structures in the stomach's acid-producing mucosa, particularly parietal cells and components associated with intrinsic factor. The damage is concentrated mainly in the gastric body and fundus and can lead over time to loss, or atrophy, of the specialized glands in these regions .^1,2

Parietal cells normally secrete hydrochloric acid and intrinsic factor, which is required for efficient vitamin B12 absorption. Progressive parietal-cell loss can therefore reduce stomach acid and impair B12 handling. Iron deficiency may also occur, sometimes before vitamin B12 deficiency, because gastric acid supports normal dietary iron absorption. The disease can alter gastrin levels and the populations of endocrine cells in the stomach .^1,2

Autoimmune gastritis is different from Helicobacter pylori gastritis, although the two can coexist and may have overlapping histologic features. It is also not identical to pernicious anemia. Pernicious anemia is a late hematologic consequence of severe vitamin B12 deficiency related to intrinsic-factor failure, while autoimmune gastritis is the underlying gastric disease and can be present long before anemia develops .^1,2