Collagenous Gastritis: A Rare Cause of Severe Iron Deficiency Anemia in a Pediatric Patient

A previously well 15-year-old male presents with a four month history of pallor, exertional palpitations, shortness of breath and headaches. This otherwise well young man had no obvious bleeding, petechiae, hematochezia, melena, hematuria, hematemesis, or hemoptysis. There was no prior history of bleeding disorder and had not been diagnosed with anemia on prior examination. He takes no medications. Family history was unremarkable and specifically, no bleeding disorders were noted. Housing is sufficient without concern for a social contribution to his symptoms. He eats a regular diet with seemingly sufficient consumption of dietary iron. Physical exam yielded stable vitals within normal limits, generalized pallor, decreased sensation of the tongue, anterior cervical lymphadenopathy, and a normal abdominal exam. Laboratory evaluation uncovered the following: a severe microcytic anemia with normal platelets, low ferritin, low iron, elevated total iron binding capacity, and an iron saturation of 1%. Peripheral smear showed microcytic anemia, anisocytosis, and poikilocytosis. Stool was hemoccult positive and H. pylori negative. Serology evaluation for celiac disease was negative. Due to the hemoccult positivity in the setting of severe microcytic anemia, endoscopy was indicated. Colonoscopy was normal, including biopsy, though a single worm was observed in the proximal colon. Esophagogastroduodenoscopy showed a friable mucosa with prominent nodularity, edema and grossly digested blood. Collagenous gastritis (CG) was confirmed via histologic examination of gastric biopsies. CG is an extremely rare disorder characterized by subepithelial deposition of collagen in the stomach. In our case, it is the root cause of the profound iron deficient anemia our patient was experiencing. Treatment is limited to symptomatic management due to the lack of pathophysiologic knowledge of CG, though multiple modalities were attempted without success. Severe iron deficiency anemia, even when caused by this difficult to treat disease, itself is highly manageable. Ultimately, we must remember to consider a gastrointestinal etiology as a part our differential diagnosis in the presence of anemia, easily screened with hemoccult testing