PSEUDOMEMBRANOUS COLITIS (Robbins pp 809)

This is when a pseudomembrane of fibrin, mucous and inflammatory debris forms on top of the areas of injured mucosa.

Pathogenesis/Aetiology: Condition is caused by exotoxins A & B of C. difficile, which is normally found in the gut, and normally occurs after a course of broad spectrum antibiotic. After antimicrobial therapy, the gut bacteria is altered, so C. difficile flourish. They release toxins, which bind to receptors on epithelial cells, inactivating RhO proteins. This breaks down actin filaments (part of the cytoskeleton of cell) and the cell retracts. In addition, toxin A causes intestinal secretion + inflammation.

Macroscopy & Microscopy: Affects colon majority of times. Yellow plaques of fibrin material present with presence of inflamed colonic mucosa. Microscopically, necrotic debris composed of fibrin adheres on top of areas of mucosal damage. The adjacent areas are normal.

Clinical features / diagnosis: diarrhea. Diagnosis by presence of cytotoxin of C. difficile in stool.

Category: Pathology Notes