Fræðigrein

Microscopic colitis (MC) is an encompassing term for two diseases; collagenous colitis and lymphocytic colitis. The colon appears normal by colonoscopy and a diagnosis is only obtained with a biopsy. The histopathology of collagenous colitis is mainly characterized by a thickening of the subepithelial basement membrane of the colonic mucosa with a band of collagen. Lymphocytic colitis is mainly characterized by an intraepithelial lymphocytosis without the collagen thickening. Even though the two diseases have a distinctive pathology their clinical symptoms are characterized by chronic watery diarrhea without bleeding. Microscopic colitis is thought to cause about 4-13% of all chronic diarrhea but their relative frequency is much higher among older people. The mean annual incidence for collagenous and lymphocytic colitis has been increasing. Steroids are the most effective treatment for microscopic colitis and budesonide is the most studied and effective therapy for MC. The aim of this paper is to give a review of two relatively new diseases which are among the most common cause of chronic diarrhea, especially among older people.

Keywords: microscopic colitis, collagenous colitis, lymphocytic colitis, diarrhea, abdominal pain, drug treatment.

Correspondence: Jón Gunnlaugur Jónasson, jongj@landspitali.is

Figure 1. Collagenous colitis. The white arrow points at the markedly thickened subepithelial collagen band. The black arrow indicates degenerated and somewhat detached surface epithelium. (Magnification x300)

Figure 2. Lymphocytic colitis. The arrows highlight lymphocytes (small dark nuclei) in amongst the surface epithelial cells. (Magnification x500)