Pyloric or Pseudopyloric Metaplasia of the Corpus Mucosa in Autoimmune Gastritis

Inclusion Criteria: * Patients who present with relevant symptoms or signs of upper gastrointestinal diseases, including, but not limited to the following: impaired gastric emptying, epigastric discomfort, postprandial bloating, early satiety, epigastric pain, acid regurgitation, dyspepsia, anemia, or vitamin B12 deficiency, or iron deficiency, are candidates to be enrolled to receive gastroscopy. Exclusion Criteria: * The exclusion criteria are as follows including use of aspirin, non-steroidal anti-inflammatory drugs, or cyclooxygenase-2 selective inhibitors for more than 3 months, or diagnosis with upper gastrointestinal cancer including esophagus, stomach, duodenum, mucosa-associated lymphoid tissue lymphoma, other gastric lymphoma, or pancreas.