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8 November 2012 - Case #257

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Thanks to Dr. Josemari Arrinda Yeregui, Bidasoa Hospital (Spain), for contributing this case and the discussion.

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Case #257

Clinical history:
A 50 year old man presented with watery diarrhea for 12 months. Endoscopy was suggestive of Crohn's disease of the right colon.

Microscopic images:

What is your diagnosis?

Click here for diagnosis and discussion:

Diagnosis: Intestinal spirochetosis and amebiasis


Microscopically, many Entamoeba histolytica trophozoites are seen, as well as a blue hazy barrier at the mucosa. This barrier is highlighted with PAS and with anti-Treponemal pallidum antibody (above).

Human intestinal spirochetosis is defined histologically by the presence of spirochetal microorganisms attached to the apical cell membrane of colorectal epithelium (Ger Med Sci 2010;8:Doc01).

Human intestinal spirochetes include Brachyspira aalborgi and Brachyspira pilosicoli. Incidence is common in poorly developed areas, but low where living standards are high. Homosexuals and HIV+ individuals are at high risk. Most patients are asymptomatic, but children, homosexual and HIV+ men are more likely to be symptomatic regardless of invasion. The bacteria can be highlighted using silver stains, PAS, Giemsa, Alcian blue (pH 2.5) and by immunohistochemistry.

Intestinal spirochetosis often coexists with other enteric pathogens, including Entamoeba histolytica (J Gastroenterol Hapatol 2007;22:64), Enterobius vermicularis, Helicobacter pylori, Shigella flexneri and Neisseria gonorrhoeae. Amebic colitis (amebiasis) resembles inflammatory bowel disease but is caused by Entamoeba histolytica protozoa. It may cause dysentery, colonic stricture, ulceration and perforation, liver abscesses up to 10 cm or be asymptomatic. Transmission is by fecal oral spread, with increased incidence in homosexuals, patients with AIDS or from the tropics (Wikipedia: Entamoeba Histolytica [Accessed 10 April 2024]).

The patient was treated with metronidazole, which covers both pathogens, which eliminated the diarrhea. The patient was subsequently diagnosed as HIV+.

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