Collagenous Gastritis Masquerading as Eosinophilic Gastritis.

A 11-year-old boy presented to the gastroenterology clinic after a 5-month history of fatigue, pallor, intermittent abdominal pain, and iron-deficiency anemia. Although the initial upper endoscopy was visually normally, the histological assessment was suggestive of eosinophilic gastritis. After multiple scopes and failed therapies, histologic analysis revealed a focus of thickened subepithelial collagen deposition suggestive of collagenous gastritis. A retrospective review of gastric biopsies using Gomori trichrome stain revealed previously unappreciated collagen deposition. This case report illustrates the benefit of performing trichrome stain on gastric biopsies in the setting of persistent or isolated gastric eosinophilia or iron deficiency anemia.