chronic autoimmune gastritisautoimmune gastritis pathologyautoimmune chronic atrophic gastritisautoimmune gastritis pernicious anemiaautoimmune gastritis mayo clinicimmune gastritissjogren's gastritiserythematosus endoscopic gastritismetaplastic atrophic gastritispernicious anemia and gastritischronic gastritis pernicious anemiaautoimmune thrombocytopenia