Microscopic colitis syndrome.

Abstract

The colorectal biopsy specimens from 30 patients with chronic watery diarrhoea but normal endoscopic and radiographic findings were studied by light microscopy, morphometry, immunohistochemistry, and two patients with electron microscopy. The histological changes in the colorectum were originally diagnosed in six patients as lymphocytic colitis and in 24 patients as collagenous colitis. The analysis of the specimens for this study could delineate three distinct groups of microscopic colitis: lymphocytic colitis (six patients), collagenous colitis without lymphocytic attack on the surface epithelium (seven patients), and a mixed form presenting with both thickening of the collagen plate and increased number of intraepithelial lymphocytes (17 patients).No transformation was seen from one type to another during follow up of six patients for four to seven years. Increased numbers of active pericryptal myofibroblasts were found with the electron microscope in one patient with mixed microscopic colitis showing also myofibroblasts entrapped within the collagen layer. Hitherto undescribed flat mucosa of the ileum was found in one patient with lymphocytic colitis and both flat mucosa and thickening of the collagen plate in the ileum were seen in one patient with the mixed form of the disease. In another patient with mixed microscopic colitis, normalisation of the colorectal morphology occurred after temporary loop ileostomy, followed by the reappearance of both diarrhoea, inflammation, and thickening of the collagen plate after the ileostomy was reversed. No association was found between non-steroid anti-inflammatory drug (NSAID) consumption and collagenous or mixed microscopic colitis. The primary cause of microscopic colitis is probably an immunological reaction to luminal antigenls, perhaps of ileal origin.

Histopathological Features of the Terminal Ileum in Lymphocytic and Collagenous Colitis: A Study of 32 Cases and Review of Literature

“…Larvol et al (21) and Einarsson et al (23) each described primary ileal villous atrophy in a patient with lymphocytic colitis. Two patients with primary ileal villous atrophy and lymphocytic colitis were described by Veress et al (7). One patient also showed features of collagenous colitis.…”

“…Seven cases of primary ileal villous atrophy have been described in the literature in association with microscopic/lymphocytic/collagenous colitis (7,20,23,24). Larvol et al (21) and Einarsson et al (23) each described primary ileal villous atrophy in a patient with lymphocytic colitis.…”

“…Evidence of chronic mucosal injury, such as crypt distortion and architectural disarray, is generally lacking (9). However, subepithelial collagen thickening is seen only in collagenous colitis (1,(3)(4)(5)(6)(7).…”

“…Prior studies of lymphocytic and collagenous colitis have identified abnormal findings in the duodenum (13,14) and jejunum (15)(16)(17)(18)(19), but only a few studies have described the changes in the mucosa of the terminal ileum (1, 7, 12, 20 -24). In these studies, the terminal ileum has been shown to have normal morphological features (1,12) or to demonstrate variable degrees of villous atrophy (7,21,23,24) with or without thickening of the subepithelial collagen table (20, 22; Table: 1). Specific quantitative references to the intraepithelial lymphocyte population are limited (12).…”

“…Lymphocytic colitis (1)(2)(3)(4) and collagenous colitis (1,(3)(4)(5)(6)(7) consist of a spectrum of related clinicopathological entities. Collagenous colitis primarily affects middle-aged and older women, who present with prolonged watery diarrhea.…”