Case Report: Scar-Like Alterations of the Gastric Mucosa Observed Under Endoscopy in Collagenous Gastritis.

Collagenous gastritis (CG) is an uncommon disorder of the digestive system, characterized by marked thickening of the subepithelial collagen band and infiltration of inflammatory cells within the lamina propria. The etiology and pathogenesis of CG remain not fully understood, and its diagnosis is contingent upon histopathological evaluation, contributing to its status as an under-recognized condition. This article presents a case involving a 35-year-old male patient of Chinese descent, whose primary clinical manifestations included upper abdominal bloating and discomfort. Endoscopic assessment revealed diffuse scar-like alterations throughout the cardia, fundus, corpus, antrum, pylorus, and duodenal bulb. Histopathological analysis using Hematoxylin and Eosin (HE) staining indicated extensive inflammatory cell infiltration in the lamina propria along with focal fibrosis. Masson trichrome staining identified a subepithelial collagen fiber band with a maximum thickness of 34 μm, thereby confirming the diagnosis of CG. The patient's clinical symptoms showed significant improvement following treatment with a modified traditional Chinese herbal decoction, Banxia Xiexin Tang (BXXXT). This case reveals the heterogeneity of endoscopic manifestations in CG, emphasizes the importance of diffuse scar-like changes as a potential endoscopic feature, and highlights the significant value of periodic endoscopic follow-up for monitoring disease progression.