Summary

• Inability to produce gastric acid. Most commonly caused by gastric atrophy. Gastric atrophy, with or without autoimmune gastritis, is present in about 15% of older people and is thought to be initiated by infection with Helicobacter pylori.
• Usually asymptomatic but may present with signs and/or symptoms of iron, cobalamin (vitamin B12), or calcium deficiency and may predispose to enteric infection with organisms such as Clostridium difficile, Salmonella, and Campylobacter.
• May interfere with the absorption of certain drugs including thyroxine, ketoconazole, itraconazole, and dipyridamole.
• The most common cause of hypergastrinaemia.
• Although the prognosis is excellent, it carries a small increased risk for the development of gastric adenocarcinoma and gastric carcinoid tumour.