RESUMO
BACKGROUND: Autoimmune atrophic gastritis (AAG) is a type of chronic gastritis that mainly affects the gastric corpus. Due to the lack of standard diagnostic criteria and overlaps with the courses of Helicobacter pylori-related atrophic gastritis, reports on the diagnostic strategy of AAG at an early stage are limited. CASE SUMMARY: A 71-year-old woman with severe anemia was diagnosed with AAG. Endoscopic views and pathological findings showed the coexistence of normal mucosa in the gastric antrum and atrophic mucosa in the gastric fundus. Serological tests showed that anti-parietal cell antibodies and anti-intrinsic factor antibodies were both positive. Immunohistochemical results, which showed negative H+-K+ ATPase antibody staining and positive chromogranin A (CgA) staining, confirmed the mechanism of this disease. After vitamin B12 and folic acid supplementation, the patient recovered well. CONCLUSION: Successful diagnosis of AAG includes serological tests, endoscopic characteristics, and immunohistochemistry for H+-K+ ATPase and CgA antibodies.