I. Acute gastritis

• Acute H. pylori infection
• Other acute infectious gastritides
  1. Bacterial (other than H. pylori)
  2. H. heilmannii
  3. Phlegmonous
  4. Mycobacterial
  5. Syphilitic
  6. Viral
  7. Parasitic
  8. Fungal

II. Chronic atrophic gastritis

• Type A: Autoimmune, body-predominant
• Type B: H. pylori-related, antral-predominant
• Indeterminate

III. Uncommon forms of gastritis

• Lymphocytic
• Eosinophilic
• Crohn's disease
• Sarcoidosis
• Isolated granulomatous gastritis
• Russell body gastritis