The changing face of chronic autoimmune atrophic gastritis: an updated comprehensive perspective.

Chronic autoimmune atrophic gastritis (CAAG) is an organ-specific autoimmune disease, which affects the corpus-fundus gastric mucosa. Although it has been described for several years, the real pathophysiological mechanisms, the natural history and the possible neoplastic complications are not completely known. Atrophy of the gastric mucosa is the endpoint of the chronic processes, with the loss of glandular cells and their replacement by intestinal-type epithelium, pyloric-type glands, and fibrous tissue. As a consequence, hydrochloric acid, pepsin and intrinsic-factor is impaired resulting in pernicious anemia. The exact causal agent is not yet known, but both genetic and environmental factors seem to play a decisive role. Moreover, the clinical onset may assume different characteristics; differently from what previously observed, recent evidence has reported the onset of CAAG at a younger age, frequently with iron deficiency anemia or upper gastro-intestinal symptoms. The diagnosis of CAAG might be challenging and usually requires the combination of clinical, serological and histopathologic data; moreover, CAAG patients are often misdiagnosed as refractory to HP eradication therapy, probably because achlorhydria might allow urease-positive bacteria other than H pylori to colonize the stomach, causing positive 13C-urea breath test results. However, biopsy is the most reliable method to evaluate the presence of metaplastic atrophic gastritis. In order to assess the severity of gastric atrophy and intestinal metaplasia, OLGA and OLGIM staging systems have been proposed and seem to correlate with the risk of developing gastric adenocarcinoma. Indeed, CAAG represents a pre-neoplastic condition, as patients with CAAG are very likely to develop either type-1 gastric neuroendocrine tumors and gastric adenocarcinomas, as well as several other neoplastic diseases. To date, the need, the intervals and cost-effectiveness of endoscopic/histological surveillance for patients with CAAG/pernicious anemia are yet to be established.