Diffuse dark brown discoloration of gastric fundic gland mucosa following proton pump inhibitor therapy.

Herein, we report a case in which diffuse dark brown discoloration was observed throughout the gastric fundic gland mucosa on endoscopy 2 years after the initiation of proton pump inhibitor (PPI) therapy. In addition, scattered dark brown spots were observed within the area of diffuse discoloration. These lesions were significantly more pronounced on the Texture and Color Enhancement Imaging mode 1. These changes were not observed before the initiation of PPI therapy or in the antrum after PPI administration. Biopsy specimens from the discolored mucosa revealed lipofuscin granules in the cytoplasm of the parietal cells. These findings suggest that the discoloration was a result of the deposition of lipofuscin due to the action of PPI on parietal cells. To the best of our knowledge, these findings have not been previously reported and are distinct from those of black spots and gastric pseudomelanosis. We believe that these new findings offer valuable insights into gastric mucosal changes associated with PPI therapy.