Long-term endoscopic changes in vonoprazan-associated web-like mucus: a rare case report with mucus culture analysis

Web-like mucus (WLM) is a recently recognized endoscopic finding associated with potassium-competitive acid blocker (P-CAB) therapy, particularly with vonoprazan (VPZ). However, its clinical significance, dose-dependency, and reversibility remain unclear. Here, we report a case of WLM that developed after VPZ treatment initiation and disappeared after dose reduction. A 78-year-old man with refractory gastroesophageal reflux disease switched from proton pump inhibitor therapy to VPZ 20 mg. Follow-up esophagogastroduodenoscopy revealed white transparent mucus resistant to water irrigation in the gastric fornix and upper body, consistent with WLM. Gastric mucus culture revealed the presence of oral commensal bacteria. Although VPZ therapy was continued, the dose was reduced to 10 mg because of improvement in reflux symptoms. Subsequent endoscopy performed 2 months after the dose reduction showed complete disappearance of the WLM. This case suggests that WLM may be a reversible gastric mucosal change associated with VPZ therapy and may exhibit dose-dependent behavior. Changes in gastric microbiota induced by profound acid suppression may contribute to its pathogenesis. Recognizing this finding is crucial since it may obscure the gastric mucosa and potentially interfere with careful endoscopic evaluation. Further studies are required to clarify the pathophysiological mechanisms and clinical implications of WLM in patients receiving P-CABs.