Gastritis refers to many forms of inflammation that affect the stomach in different ways. Gastritis can be classified by its origin, how it occurs or what part of the stomach it affects. Some of these classifications overlap. Some of the most commonly classified types include:

• Erosive gastritis. This is the most common form of gastritis. Acid or other factors can inflame, damage and wear away the inner lining of the stomach (gastric mucosa).  It may be acute or chronic, but is usually chronic.
  
  
• Acute stress gastritis. Results from severe illness or injury. This is most common in patients in intensive care units, especially those with respiratory failure, sepsis (infection in the blood), kidney failure, severe burns, peritonitis or neurologic trauma. It is not known why these problems, which generally do not directly affect the stomach, lead to gastritis. However, the link may be related to decreased blood flow to the stomach or an impairment of the ability of the gastric mucosa to protect and heal itself.
  
  
• Atrophic gastritis. In this chronic form of gastritis, the gastric mucosa becomes very thin (atrophy) and many or all of the cells that produce digestive acids and enzymes are lost. This occurs due to an autoimmune problem in which antibodies attack the body’s own tissues (autoantibodies) or in elderly patients for unknown reasons. It may also be caused by infections or following a partial gastrectomy (surgical removal of part of the stomach).
  
  
• Eosinophilic gastritis and plasma cell gastritis. In these extremely rare types of gastritis, specific types of white blood cells (eosinophils or plasma cells) build up in the wall of the stomach. The cause of this is generally not known, but it could be due to an allergic reaction. These are usually chronic.
  
  
• Ménétrier's disease. In this rare, chronic form of gastritis, giant folds of tissue develop in the stomach wall. These folds may be prone to inflammation or ulcers and generally cause the acid and enzyme-secreting glands in the stomach to waste away, resulting in the loss of certain proteins (e.g., albumin). It most frequently affects men between the ages of 30 and 60. Ménétrier’s disease is also known as giant hypertrophic gastritis or protein losing gastropathy.