Histologic features of cytomegalovirus enteritis in small bowel allografts

Cytomegalovirus (CMV) is one of the most common viral infections to affect solid organ transplant patients, most frequently owing to reactivation of a latent infection as a result of immunosuppression. CMV enteritis (CE) may enter into the differential diagnosis of acute rejection in biopsies of small bowel (SB) allografts, where differentiation is important due to disparate therapies.

The aim of this study was to identify histologic features in SB allografts that may suggest CE.

The case files for a single institution were queried for all cases of SB mucosal biopsies with cells positive by CMV immunoperoxidase staining. Morphologic and clinical information was reviewed.

Six biopsies demonstrating immunoperoxidase-confirmed CE were identified in a retrospective review of the records of a single institution. A common predisposing factor was the administration of high-dose steroids within a month before CE diagnosis. Most cases (66%) displayed a demarcated area of villous/crypt loss with an abundance of plasma cells and lymphocytes and a paucity of eosinophils. One case showed an acute enteritis-like pattern of injury, corresponding with a higher number of CMV-positive cells. CMV inclusions were visible on hematoxylin-eosin stains in all but 1 case. In no case were histologic criteria for acute cellular rejection met.

The presence of circumscribed area of mucosal injury with few eosinophils or an acute enteritis pattern should prompt the identification of viral inclusions or the acquisition of a CMV immunostain.