Since the discovery of Helicobacter pylori (H. pylori), numerous studies have 
considered the possibility that it plays a role in different extragastric 
diseases. Most of these studies may be classified as epidemiological studies or 
investigations of H. pylori eradication, but there are also case reports and in 
vitro studies. This review reveals the limitations common to most of them. 
Idiopathic thrombocytopenic purpura is the disease for which the strongest 
association with H. pylori infection has been shown. Data are also accumulating 
about the role of H. pylori infection in idiopathic iron deficiency anemia and 
chronic idiopathic urticaria. Interesting results show that H. pylori infection 
affects atherosclerosis and is weakly associated with ischemic heart disease and 
stroke. Moreover, CagA-positive H. pylori strains may play a role in the natural 
history of atherosclerotic stroke. Recent studies suggest a link between H. 
pylori and Parkinson's disease. Preliminary data indicate that H. pylori 
infection impairs gastric ghrelin production and may influence nutritional 
status. The association between H. pylori infection and other extragastric 
diseases remains controversial. H. pylori infection may cause extragastric 
manifestations directly or indirectly, by various mechanisms including atrophic 
gastritis, the release of inflammatory mediators, molecular mimicry, and 
systemic immune response. Evidence suggests that anti-H. pylori therapy improves 
idiopathic thrombocytopenic purpura (significant increase of platelet count in 
half of the cases), iron-deficiency anemia, and chronic urticaria (30% remission 
rate), but the data from randomized controlled trials are insufficient to 
confirm these positive effects.