Histopathology of typhoid enteritis: morphologic and immunophenotypic findings

Enteric fever is a systemic illness caused by Salmonella infection, with S. typhi, S. paratyphi, and S. enteritidis being the most common serotypes. Humans are the only reservoir for S. typhi, and its predilection for the ileum is due to the fact that organisms enter the body by translocation across specialized Peyer's patch epithelium and then proliferate in the mucosal macrophages. The lesions in bowel and mesenteric lymph nodes are distinctive and mimic Kikuchi-Fujimoto disease and Rosai-Dorfman disease as well as infections caused by some non-salmonella bacteria. The four cases presented in this report, two culture-confirmed, all exhibited ileal mucosal hypertrophy caused by a neutrophil-poor monocyte/macrophage-rich hyperplasia. Though diffuse areas were present, much of the lesional proliferation was nodular, representing macrophage infiltration and colonization by the monocytes and macrophages. Immunophenotypic studies, which showed a CD68+, lysozyme+, UCHL-1+, OPD4-, CD4-, s100- profile, were helpful in distinguishing these lesions from other processes, including Kikuchi-Fujimoto disease and Rosai-Dorfman disease. Although rare in developed countries, enteric fever should be considered in any patient with recent travel to endemic areas and in the context of illness thought to be related to contaminated foods.