Case 71 - Discussion

Uploaded: 2007-07-25, Updated: 2007-07-25




Collagenous Colitis

  • Microscopic colitis is  used to describe both lymphocytic colitis (LC) and collagenous colitis (CC), and these conditions should be considered in any patient with unexplained nonbloody diarrhea. Patients undergoing either sigmoidoscopy or colonoscopy for unexplained diarrhea who have normal endoscopic findings should have biopsy samples taken to diagnose or rule out either form of microscopic colitis.

  • LC and CC are relatively rare conditions that are diagnosed when a patient with chronic watery nonbloody diarrhea has an endoscopically or radiographically normal colon, but colonic biopsies show unique inflammatory changes. Because the mucosa is not ulcerated or otherwise disrupted, the diarrhea generally does not contain blood or pus.

  • No definite etiology has been determined. Many drugs may cause diarrhea as an adverse effect, nonsteroidal anti-inflammatory drugs (NSAIDs) show a strong trend (p=0.057) toward increasing the risk of CC. Antidepressant selective serotonin reuptake inhibitors (SSRIs) as a group increase the risk of CC, but, among this class of medications, sertraline alone significantly increases the risk of LC.  HLA-A1 is more frequent in patients with LC (67%) than in controls (28%) or in patients with CC (26%).  Approximately 50% of both patients with CC and patients with LC may have circulating autoantibodies, especially antiparietal cell, antithyroglobulin, and antimicrosomal antibodies.

  • The characteristic feature of LC is an infiltration of lymphocytes into the colonic epithelium.  CC shares the histologic features of LC but additionally demonstrates a thickened subepithelial collagen layer (usually >10 Ám) in the lamina propria. LC and CC have been suggested to represent different phases of a single pathophysiologic process, with LC possibly being a precursor or earlier phase of CC. Surface epithelium shows a chronic inflammatory infiltrate of plasma cells, lymphocytes, and eosinophils in the lamina propria. Intraepithelial lymphocytosis, with greater than 20 lymphocytes per 100 epithelial cells, is pathognomonic of the diagnosis of LC. Epithelial cell damage is demonstrated by cell flattening, subepithelial blebs, and denuded epithelium. Crypts typically have normal architecture, unlike Crohn disease or ulcerative colitis.

The Johns Hopkins Division of Gastroenterology and Hepatology

  • The Johns Hopkins Division of Gastroenterology and Hepatology