A Case Report of Autoimmune Gastritis Associated With Polyendocrine Syndrome Type III Mimicking Refractory H. pylori Infection

A 60-year-old woman had persistent positive urea breath test (UBT) results despite three courses of <i>Helicobacter pylori</i> (<i>H. pylori</i>) eradication therapy. Endoscopy revealed extensive atrophic gastritis with a characteristic "reverse atrophic pattern" affecting the gastric corpus while sparing the antrum. Active <i>H. pylori</i> infection was excluded; however, positivity for anti-parietal cell and anti-intrinsic factor antibodies confirmed autoimmune gastritis (AIG). Further screening identified anti-glutamic acid decarboxylase antibodies and thyroid autoantibodies, leading to a diagnosis of autoimmune polyendocrine syndrome type III. This case highlights the potential for false-positive UBT results in AIG, emphasizing the importance of screening for associated autoimmune conditions.