|Classification and external resources|
Microscopic colitis refers to two medical conditions which cause diarrhea: collagenous colitis and lymphocytic colitis. Both conditions are characterised by the following triad of clinicopathological features:
Patients are characteristically, though not exclusively, middle-aged females. They present with a long history of watery diarrhoea, which may be profuse. There is a higher incidence of autoimmune diseases, for example arthritis, Sjögren's syndrome, and coeliac disease, in patients with microscopic colitis. There are reports of associations with multiple drugs, especially proton pump inhibitors, H2 blockers, and non-steroidal anti-inflammatory drugs (NSAIDs).
Colonoscopy is normal or near normal. The changes are often patchy, so multiple colonic biopsies must be taken in order to make the diagnosis. A full colonoscopy is required, as an examination limited to the rectum will miss cases of microscopic colitis.
The hallmark of microscopic colitis is an increase in inflammatory cells (i.e., lymphocytes) in colonic biopsies with an otherwise normal appearance and architecture of the colon. Inflammatory cells are increased both in the surface epithelium ("intraepithelial lymphocytes") and in the lamina propria. In lymphocytic colitis, these are the only abnormal features.
The prognosis for lymphocytic colitis and collagenous colitis is good, and both conditions are considered to be benign. The majority of people afflicted with the conditions recover from their diarrhea, and their histological abnormalities resolve.
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- Mullhaupt B, Güller U, Anabitarte M, Güller R, Fried M (1998). "Lymphocytic colitis: clinical presentation and long term course". Gut 43 (5): 629–33. doi:10.1136/gut.43.5.629. PMC 1727313. PMID 9824342.