Gastric Hyperplastic Polyp with Helicobacter suis-infected Gastritis.

A 56-year-old man who owned dogs and cats and had raised pigs as a child underwent upper gastrointestinal endoscopy. A mild, flat bulge that had been visible three years earlier (Picture 1A, arrow) had grown into a hemispherical polyp in the antrum (Picture 1B, arrow, Picture 1C). Although regular arrangement of the collecting venule was seen in the gastric body (Picture 2A), mild gastritis was seen in the antrum (Picture 2B). The polyp was histologically consistent with a gastric hyperplastic polyp (HP) (Picture 3A). Furthermore, organisms longer, larger, and with a more tightly spiral shape (about 4-8 turns) (Picture 3B) than Helicobacter pylori, suggesting non-H. pylori Helicobacter (NHPH), were found in the gastric pits of the HP and gastric mucosa of the antrum. This organism was positive on immunostaining with anti-Helicobactor suis vacA paralog antibody (Picture 3C). A serum anti-H. pylori immunoglobulin G antibody test and urea breath test were negative. The gastritis improved, and the HP shrank after administration of vonoprazan 20 mg, amoxicillin 750 mg, and clarithromycin 400 mg twice a day for 7 days (Picture 1D, arrow). NHPH infection is considered zoonotic and induces mild gastritis (1). This case shows that gastric HP, which is usually caused by severe atrophic gastritis (2), can develop even in cases of mild gastritis due to NHPH infection.

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The authors state that they have no Conflict of Interest (COI).