Acute gastritisErosions can be caused by:- NSAIDs – ↓ PGE₂ → ↓ gastric mucosa protection- Burns (Curling ulcer) – hypovolemia → mucosal ischemia- Brain injury (Cushing ulcer) – ↑ vagal stimulation → ↑ ACh → ↑ H⁺ production- Especially common among alcoholics and patients taking daily NSAIDs (eg, patients with rheumatoid arthritis).

Chronic gastritis- Mucosal inflammation, often leading to atrophy (hypochlorhydria → hypergastrinemia) and intestinal G-cell metaplasia (↑ risk of gastric cancers).- H pylori: Most common. ↑ risk of peptic ulcer disease, MALT lymphoma. Affects antrum first and spreads to body of stomach.- Autoimmune: Autoantibodies to parietal cells and intrinsic factor. ↑ risk of pernicious anemia. Affects body/fundus of stomach.