[Helicobacter pylori infection and gastric diseases--pathogenesis and effects of eradication].

H. pylori infection is associated with major gastroduodenal diseases, i.e. peptic ulcer, cancer and MALT lymphoma in the stomach. The pathogenesis of H. pylori in these diseases has been elucidated. Non-atrophic diffuse antral gastritis is correlated with duodenal ulcer and multifocal atrophic gastritis is correlated with both gastric ulcer and cancer. It is well known that Japanese tend to have multifocal atrophic gastritis. H. pylori eradication therapy dramatically reduces the recurrence rates of gastroduodenal ulcers in humans and bacterial eradication for peptic ulcer patients has been recommended in many countries. Mongolian gerbils have provided an excellent model of gastric carcinogenesis and H. pylori enhanced (promoted) chemical carcinogen-induced carcinogenesis in the stomach using this model. H. pylori eradication reduced the incidence of gastric cancer in the Mongolian gerbil model. It was a recently discovered that a transforming clone carrying the translocation t (11;18) (q21;q21) forms a MALT lymphoma, the growth of which is independent of H. pylori and will not respond to bacterial eradication. In the early stage, the tumor can be successfully treated by eradication, but at a later stage additional genetic abnormality in the lymphoma may show no response to H. pylori eradication therapy.