Collagenous gastritis is an extremely rare disorder of unknown etiology, To date, fewer than ten cases have been reported in the literature. The condition is characterized by deposition of a subepithelial collagen band greater than 10 |im in thickness. The disorder was originally described by Colletti and Trainer in a 15-year-old girl with refractory H. pylori-negative chronic gastritis.55 It has been reported either as an isolated entity or with synchronous collagenous colitis, collagenous duodenitis, lymphocytic colitis or celiac disease. Clinical features, such as epigastric pain, vomiting, anorexia, postprandial fullness and weight loss are reported. Endoscopic findings include diffuse nodularity, patchy or diffuse erythema, erosions and frank ulcers with hemorrhage. The diagnosis relies on mucosal histology, usually of the fundus and corpus, sharing discontinuous subepithelial collagen deposition with entrapped capillaries and fibroblasts, in association with mild glandular atrophy and mixed inflammatory infiltrate in the lamina propria, including lymphocytes, neutrophils, degranulating eosinophils and mast cells.56 Depending on the extension of the inflammatory infiltrate, the corresponding surface epithelium may show an increased number of intraepithelial lymphocytes and degenerative changes.
Three major pathogenic theories have been proposed for the increased subepithelial collagen deposition: inflammatory origin, abnormality of the pericryptal collagen sheath and autoimmune injury. It has been suggested that an initial stimulus caused by an infective agent, drug or food allergen may damage the mucosal surface and, in susceptible individuals, determine subepithelial collagen deposition irrespective of the course of gastritis in the rest of the mucosa. However, this theory remains to be demonstrated.
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