S3167 Clinical and Histopathological Characteristics of Patients With Autoimmune Gastritis at a U.S. Tertiary Care Center

Introduction: Autoimmune gastritis (AIG) is a chronic autoimmune condition of the stomach with a worldwide prevalence of 0.5-4.5%. AIG has been primarily studied in European and East Asian populations. To our knowledge, few studies have characterized patients with AIG in the United States (U.S.). We describe the clinical, endoscopic and histopathological characteristics of patients with AIG at a U.S. tertiary care center. Methods: In this retrospective cohort study, we included a random cohort of adult patients who underwent upper endoscopy esophagogastroduodenoscopy (EGD) between 2010 and 2022, and who had gastric biopsies demonstrating histopathologic features consistent with AIG, defined as corpus atrophy with enterochromaffin-like cell hyperplasia. Patients with history of reflux esophagitis, gastrectomy, or Helicobacter pylori gastritis were excluded. Demographic, clinical, laboratory, endoscopic and pathology characteristics were collected. Descriptive statistics were applied. Results: A total of 126 patients were included. Seventy-five percent were women and 72% White. Mean age at the time of EGD diagnostic of AIG was 60 ± 7 years. Ninety-three percent of patients had gastrointestinal (GI) symptoms, with abdominal pain (45%) and heartburn (42%) being the most common. Among all autoimmune disorders, Hashimoto thyroiditis was the most common in 23% of patients. Sixty-three percent (62/98) and 69% (64/92) had vitamin B12 and iron deficiency, respectively. Out of 94 patients tested for AIG serologies, 83% had either a positive intrinsic factor or parietal cell antibody. Sixty-two percent had gastric intestinal metaplasia, 9.5% had a gastric neuroendocrine tumor type 1, 2 had gastric dysplasia, and 1 patient had gastric adenocarcinoma. Conclusion: In our U.S. cohort of AIG patients, most had GI symptoms with heartburn, likely functional, being a common one, suggesting that AIG may be under-recognized in patients with nonspecific upper GI complaints. Our findings of prevalent vitamin B12 and iron deficiencies, as well as pre-neoplastic and neoplastic lesions at diagnosis, emphasize the need for early disease recognition to improve neoplastic outcomes through surveillance, and implement periodic screening for thyroid disease and nutritional deficiencies.