H. pylori infection and extra-gastroduodenal diseases.

Helicobacter pylori infection is the principal cause of peptic ulcer disease, gastric adenocarcinoma and gastric mucosa-associated lymphoid tissue lymphoma. Recent studies have shown that it may interfere with many biological processes and determine or influence the occurrence of many diseases outside the stomach. Currently, the role of H. pylori in idiopathic thrombocytopenic purpura and iron deficiency anemia is well documented. Emerging evidence suggests that it may also contribute to vitamin B12 deficiency, insulin resistance, metabolic syndrome, diabetes mellitus and non-alcoholic liver disease. Additionally, it may increase the risk of acute coronary syndrome, cerebrovascular disease, neurodegenerative disease and other miscellaneous disorders. Different pathogenic mechanisms have been hypothesized, including the occurrence of molecular mimicry and the induction of a low-grade inflammation. This review summarizes the results of the most relevant studies on the extra-gastroduodenal manifestations of H. pylori infection.