Context: The finding of increased intraepithelial lymphocytes with normal villous architecture (Marsh I lesion) is seen in up to 3% of duodenal biopsies. The differential diagnosis includes a wide range of possibilities, including celiac disease, bacterial overgrowth, nonsteroidal antiinflammatory drug damage, reaction to Helicobacter pylori infection, tropical sprue, and chronic inflammatory bowel disease.
Objectives: To highlight the histologic features of the Marsh I lesion, review the diseases and conditions associated with that finding, and to provide pathologists with a rationale and a template for how to identify and report such cases.
Data sources: A review of the literature regarding the histologic features and clinical associations of Marsh I lesions.
Conclusions: Marsh I lesions are a nonspecific finding associated with a number of disease conditions. Historically, between 9% and 40% of cases have been shown to represent celiac disease. Current data do not suggest histologic features to differentiate between diseases associated with this histologic change.