Retrovirus Pseudomembranous Atrophic Enteritis caused by Suicidal Emperipolesis; A Light and Ultrastructural Study

Benign retroviral infections are common but are usually not recognized. This histologic and ultrastructural study identifies such an infection that became clinically evident in the small bowel following a partial colectomy for multiple micro invasive adenomas. Suspected is a low-grade retroviral infection of myeloid progenitor cells activated by inflammatory cytokines released by the operative procedure. Multiple infected neutrophils migrated to the small bowel adjacent to the operative anastomosis and through emperipolesis entered the luminal facing enterocytes. Budding of the retrovirus beginning at the neutrophil cell membrane within enterocytes assembled an immature retrovirus virus lacking a central core because translational and transcriptional viral events were not possible in the organelle poor and nuclear damaged neutrophils. Apoptosis of the infected neutrophil released toxic products and water produced in the mitochondria that distended the vacuoles encircling the neutrophils. There disruption spilled these contents directly into enterocyte cytoplasm producing collateral organelle injury that killed and detached surface enterocytes. This effaced the intestinal villi to produce atrophic and pseudomembranous enteritis with ulcers and bowel perforations. Conclusion: The incomplete assembly of retrovirus in neutrophils rendered the virus non-infective but suicidal emperipolesis in neutrophils assembling retrovirus grouped in enterocytes created the collateral damage that caused the enteritis. This article is the first to report this suicidal variant of emperipolesis and its causative retroviral enteritis.