Helicobacter pylori and hematological disorders.

Helicobacter pylori (H. pylori) is one of the most common worldwide infections, which can affect both adults and children. The prevalence of this bacterium is variable in different countries, depending on various hygienic and socioeconomic conditions and living customs. The major damaged tissues of the infection are in the upper gastrointestinal tract, causing gastritis, gastric and duodenal ulcer and gastrointestinal malignancy. Nevertheless, other disorders are associated with this pathogen, including several hematological diseases, such as iron deficiency anemia, immune thrombocytopenia and vitamin B12 deficiency. A huge of data in literature support these associations, enough to recognize them in the last Maastricht V/Florence Consensus Report by European Study Group. The pathogenic mechanisms underlying the linkage between H. pylori and these hematological disorders are not clearly identified, but certainly the good hematological response reaches after eradication therapy confirm a central role of the bacterium in this scenario. Instead, the pathogenic mechanisms of H. pylori infection, which lead to the occurrence of mucosa-associated lymphoid tissue (MALT) lymphoma are clearer and more consolidated; so much that nowadays eradication therapy alone represents the only treatment in this disorder, when localized and with a concomitant H. pylori infection. This review focuses on the hematologic diseases related to H. pylori, particularly on iron deficiency anemia, vitamin B12 deficiency, immune thrombocytopenia and gastric MALT lymphoma.