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Case of the Week #213

10 August 2011 Case of the Week #213

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Case of the Week #213

Clinical History:

A 48 year old man had prolonged diarrhea, with a clinical impression of inflammatory bowel disease or microscopic colitis. A colonic biopsy was obtained.

Micro images:


Row 1: H&E
Row 2: PAS

What is your diagnosis?


Intestinal Spirochetosis


Sections show colonic mucosal biopsies with a lamina propria that is mildly expanded by inflammatory cells including eosinophils and mononuclear inflammatory cells. The mucosal glands appear normal under low power, but on high power the luminal surface shows a "blue fringe," which is strongly positive with PAS where filamentous organisms are present.

Intestinal spirochetosis is colonization of the colon by relatively non-pathogenic spirochetes. It is seen in 3-10% of normal patients, and is associated with anal intercourse, HIV and lower socioeconomic conditions (Ger Med Sci 2010 Jan 7;8:Doc01). It may occur in children (Pediatr Dev Pathol 2010;13:471), who often have abdominal symptoms (Am J Clin Pathol 2003;120:828). Intestinal spirochetosis may cause persistent diarrhea, possibly due to blunting and destruction of microvilli (Am J Clin Pathol 1986;86:679).

As in this case, histology shows an accentuation of the luminal border by spirochetes, which produce a blue line on H&E between the microvilli of the covering epithelium (Pathologe 2003;24:192). The spirochetes are accentuated by silver stains (Warthin-Starry, Dieterle), as well as PAS, Giemsa and Alcian-blue (pH 2.5). There is usually minimal inflammation present.

Electron microscopy shows long coiled bacteria adherent to the microvilli:

EM images of intestinal spirochetosis

Symptomatic patients are treated with metronidazole.

Nat Pernick, M.D., President
and Liz Parker, B.A., Associate Medical Editor
PathologyOutlines.com, Inc.
30100 Telegraph Road, Suite 408
Bingham Farms, Michigan (USA) 48025
Telephone: 248/646-0325
Email: NatPernick@Hotmail.com
Alternate email: NatPernick@gmail.com