H. pylori infection causes certain cancers and other illnesses.
H. pylori infection is a major cause of stomach (gastric) cancer. H. pylori causes chronic gastritis, which is thought to be the first step in the development of stomach cancer. H. pylori infection is a necessary, but not the only, cause of adenocarcinoma, which is the most common type of cancer that occurs in the non-cardia regions of the stomach. The cardia region of the stomach is the small, upper part of the stomach near the esophagus. The non-cardia regions are the remaining parts of the stomach. Adenocarcinoma accounts for up to 95% of all stomach cancers.
Less than 3% of people with H. pylori infection develop stomach cancer.
H. pylori infection is associated with a higher risk of MALT lymphoma of the stomach. This is a type of non-Hodgkin lymphoma (NHL). MALT lymphoma of the stomach accounts for less than 2% of all stomach cancers. Nearly all MALT lymphomas of the stomach are related to H. pylori infection. People infected with H. pylori have a low risk of developing MALT lymphoma (less than 1%).
H. pylori has been linked with other cancers, such as pancreatic and colorectal cancer, but there is not enough evidence to say for sure whether or not it is a risk factor for these cancers.
There is some evidence that H. pylori may also help prevent some childhood diseases, such as asthma. It may also prevent adult diseases, such as esophageal adenocarcinoma. More research is needed to confirm these findings.