Two Main Causes of Gastritis

The two most common causes of gastritis are Helicobacter pylori infection and nonsteroidal anti-inflammatory drugs (NSAIDs) use. 1

H. pylori-Associated Gastritis

H. pylori is the most important factor in the pathogenesis of chronic gastritis, present in 71-95% of all gastric cancer cases 1
H. pylori infection causes persistent active gastritis that may progress to atrophic gastritis, intestinal metaplasia, and eventually gastric cancer 2
The infection increases gastric cancer risk by approximately 2.5-fold, with some studies showing up to 6-fold increased risk 2
H. pylori eradication reduces the risk of gastric cancer development, especially when performed before the development of preneoplastic conditions 1
The pattern of gastritis caused by H. pylori can affect acid secretion - antral-predominant gastritis leads to increased acid production, while body-predominant gastritis causes decreased acid production 1

NSAIDs can cause a distinct form of gastritis known as "chemical gastritis" characterized by foveolar hyperplasia, muscle fibers in the lamina propria, edema, and vasodilation 3
NSAID-associated gastric ulcers can develop independently of H. pylori infection, representing a major subset of peptic ulcers that do not require H. pylori for their development 4
Peptic ulcers associated with NSAIDs occur more commonly in patients with either chemical gastritis or H. pylori infection 3
Regular NSAID intake may modify the inflammatory process in the gastric body, leading to a lower frequency of atrophic gastritis 5
Peptic ulceration is uncommon in the absence of either H. pylori or recent NSAID use 5

Autoimmune gastritis is the third major cause of gastritis, though significantly less common than H. pylori-associated gastritis 1
Autoimmune gastritis has an estimated prevalence of 0.5-2% compared to up to 15% for all forms of atrophic gastritis 1
It is characterized by autoantibodies against parietal cells and intrinsic factor 1
Autoimmune gastritis is more common in women and increases with age 1
It is strongly associated with other autoimmune diseases, particularly autoimmune thyroid diseases (Hashimoto's thyroiditis) 6
Pernicious anemia is a late-stage complication of autoimmune gastritis characterized by vitamin B-12 deficiency and macrocytic anemia 1

H. pylori gastritis can lead to peptic ulcer disease, atrophic gastritis, and gastric cancer 1
Atrophic gastritis is considered the first step in a multistep precancerous cascade that can lead to gastric adenocarcinoma 1
The risk of progression from atrophic gastritis to gastric adenocarcinoma ranges from 0.1% to 0.3% per year 1
Corpus-predominant H. pylori gastritis substantially increases the risk for gastric cancer 1
Autoimmune gastritis increases the risk of type 1 gastric neuroendocrine tumors due to hypergastrinemia resulting from parietal cell loss 1
Patients with atrophic gastritis should be evaluated for iron and vitamin B-12 deficiencies, especially if corpus-predominant 1

H. pylori infection can be diagnosed through non-invasive tests such as urea breath test and monoclonal stool antigen tests 1
In patients with autoimmune gastritis, testing for antiparietal cell antibodies and anti-intrinsic factor antibodies can assist with diagnosis 1
All individuals with atrophic gastritis should be assessed for H. pylori infection 1
Patients with unexplained iron or vitamin B-12 deficiency should be evaluated for atrophic gastritis 1