Introduction: Collagenous gastritis (CG) is a rare, idiopathic disorder first described in 1989. It is characterized by gastric subepithelial collagen deposition greater than 10μm with associated lamina propria inflammation composed of lymphocytes, plasma cells, and eosinophils. We report a case of a 61-year-old man who presents to clinic with a 13-month history of nausea, early satiety, post-prandial pain, and a 36 lb weight loss. The physical exam was notable for mild, generalized abdominal tenderness. Laboratory studies including a celiac panel, Helicobacter pylori, and autoimmune panel were all normal. Esophagogastroduodenoscopy demonstrated diffuse friability of gastric and duodenal mucosa. Gastric histology demonstrated an increased chronic inflammatory infiltrate with collagen deposition. Chronic duodenitis was also seen with normal villi and without collagen deposition. Colonic samples showed no evidence of microscopic colitis or inflammatory bowel disease. The patient was treated with an indefinite course of pantoprazole 40 mg daily and sucralfate 1g QID for the first month. The patient’s nausea, vomiting and pain resolved within 2 months. However, the patient continued to have early satiety, with an electrogastrogram demonstrating bradygastria. He was successfully treated with 3-month course of domperidone. At the 3-year follow up, the patient’s weight was stable without additional GI symptoms. CG can present in children and young adults from the ages of 2 to 22, and in older adults from the ages 35 to 77 with a slight female predominance overall. Adult patients can present with abdominal pain, chronic diarrhea, malabsorptive symptoms, and protein losing enteropathy. They are also more likely to have associated autoimmune diseases and intestinal disease such as collagenous colitis. The most favored theory suggests that the pathognomonic collagen deposition is secondary to chronic inflammation. Due to its rather nonspecific presentation it is diagnosed by the histopathologic examination of gastric mucosal biopsies. The gross endoscopic findings include erythema, erosions, ulcerations and hemorrhages in the gastric body and fundus. The subepithelial collagen deposition is commonly highlighted with a Masson trichrome stain. Given these pathologic findings, anti-inflammatory and anti-secretory measures encompass the most common treatment approaches. Corticosteroids, proton pump inhibitors, histamine-2 blockers, and dietary restrictions have all been attempted with variable success. CG’s wide array of clinical presentations and association with common autoimmune conditions makes it clinically relevant for the gastroenterologist.