S6453 The Uncommon Culprit: Helicobacter heilmannii Gastritis in a Young Adult With Significant Nausea and Weight Loss

Introduction: Helicobacter heilmannii is a rare zoonotic gastric pathogen distinct from Helicobacter pylori. Though both can cause chronic gastritis, H. heilmannii is less frequently encountered in clinical practice, often underdiagnosed due to poor sensitivity of standard non-invasive tests. Infections are thought to be transmitted from animals, particularly cats and dogs. This case highlights the importance of considering uncommon infectious etiologies in young patients with persistent upper gastrointestinal symptoms and unexplained weight loss. Case Description/Methods: A 19-year-old woman presented with 45 pounds of unintentional weight loss over 1 year and persistent nausea following tonsillectomy. She denied vomiting, abdominal pain, disordered eating, travel, or other systemic symptoms. body mass index was 22. Medical history was unremarkable, and she was not on any medications. Notably, she lived with several pets including cats and a dog. Esophagogastroduodenoscopy (EGD) showed a small hiatal hernia with otherwise normal mucosa. Duodenal biopsies were negative for celiac disease. Gastric biopsies revealed chronic active gastritis with spiral-shaped organisms consistent with H. heilmannii; there was no evidence of intestinal metaplasia, dysplasia, or carcinoma. Prior to EGD, her stool antigen and urea breath testing for H. pylori were negative. The patient was treated with 2-week quadruple therapy: bismuth subsalicylate 525 mg four times a day, metronidazole 250 mg four times a day, doxycycline 100 mg twice a day and pantoprazole 40 mg daily. At 1-month follow-up, she reported marked improvement in her nausea with improvement of her nutrition and gained weight. Discussion: H. heilmannii is an uncommon but clinically relevant cause of chronic gastritis. Unlike H. pylori, it is not reliably detected with stool antigen or urea breath testing and requires histological identification on gastric biopsy. Its zoonotic origin and association with pet exposure are important diagnostic clues. Though most infections are self-limited, H. heilmannii has been linked to peptic ulcers and gastric mucosa-associated lymphoid tissue lymphoma in rare cases. In patients with persistent upper GI symptoms, significant weight loss, and negative non-invasive testing for H. pylori, gastric biopsy remains essential. This case illustrates the need to broaden the differential diagnosis to include rare pathogens like H. heilmannii, especially in patients with animal exposure. Early identification enables timely treatment and prevents complications.