Supplementary Material for: Coexisting Collagenous Sprue and Celiac Disease: A Case Report

Introduction: Collagenous sprue (CS) is an extremely rare enteropathy of unknown etiology and if untreated, can lead to substantial morbidity and mortality. CS often co-presents with celiac disease. The presence of a subepithelial collagen band on histology differentiates CS from celiac disease, as both have villous blunting. The management of the two diseases is different, and thus it is critical that the proper diagnosis of CS is made promptly to prevent complications. Case Presentation: We present a case report of collagenous sprue in an elderly male who was initially diagnosed with celiac disease alone before returning to care years later with unresolved gastrointestinal symptoms. Conclusion: Clinicians must verify that CS has been ruled out following a celiac disease diagnosis. In regard to CS’s mechanism, CS’s high frequency of comorbid autoimmune conditions and its robust response to corticosteroids support an immune-mediated process. Future research should continue to aim to elucidate the mechanism as it would allow for a more targeted approach to treatment, such as anti-fibrotic or specific immunomodulator therapy.