Atypical presentation of pseudomembranous colitis localized in adenomatous polyps

Abstract

The most frequent cause of pseudomembranous colitis is Clostridium difficile (C. difficile) infection. This type of colitis is characterized by an endoscopic pattern of numerous small, yellowish or whitish plaques diffusely distributed, which typically compromises the rectum extending to proximal colon. Occasionally, the pseudomembranes compromise only the transverse or right colon, but their exclusive localization over polyps has not been reported. In this case report we have described a patient with symptoms compatible with C. difficile infection and positive for C. difficile toxigenic culture. Colonoscopy examination showed two small polyps with a whitish surface, and histopathological analysis confirmed them to be pseudomembranes over tubular adenomas. The rest of the colonic mucosa was normal and no other cause was demonstrated. We suggest that this particular distribution might be due to a higher affinity for dysplastic cells such as adenomatous polyps of colon by C. difficile and/or its toxins.

Keywords: Adenomatous polyps; Antibiotic-associated colitis; Clostridium difficile; Clostridium difficile infections; Pseudomembranous colitis.

Figure 1

Colonoscopy images showing two polyps, 4 and 6 mm in size, in the right colon with adherent whitish surface. A: Polyp of 6 mm; B: Polyp of 4 mm. The mucosa round the polyps and in the rest of colon is normal.

Figure 2

Low power view of a mucosal fragment. Histopathology shows: at the bottom, tubular structures lined by columnar epithelial cells with pseudostratified nuclei, consistent with low grade tubular adenoma (black arrow); at the top, ballooned crypts and intercrypt necrosis, an exudate featuring the classical “volcano” lesion (red arrow) surrounded by a laminated pseudomembrane composed of neutrophils, mucin and fibrin (hematoxylin and eosin, x 100).