[Colo-rectal spirochetosis: is it an anatomo-pathologic entity?].

Nineteen colorectal biopsy specimens, stained by Hematein-Eosin-Safran (HES), were examined by light microscopy and showed a thick, blue and fuzzy brush border. Without any further microbiologic investigation, this histologic feature is considered strongly suggestive of colorectal spirochetosis. Our study concerned 19 male patients aged between 35 and 68 years, who had no risk factor for HIV infection, but who belonged to these three groups: (a) those suffering from chronic diarrhea; (b) those without intestinal symptoms; (c) those who had a colonic tumor removed. Rectal biopsy specimens were also taken from a control group of 35 patients seropositive for HIV-1. This thickening, which measured 3-7 microns, showed some variation within the same patient but did not depend on the site of the biopsy. It appeared as a blue fuzzy band on HES stain, was purple on Periodic-Acid-Schiff stain and basophilic after Giemsa stain. Silver stain by Warthin-Starry method confirmed the presence in three cases of numerous spirochetes attached to the epithelial surface. Two of the three patients had no symptom. In the control group, a thickening of the brush border, was observed in only one case, but no spirochete by silver stain was seen. The thickened blue, fuzzy brush border of the colonic mucosa is not a specific criterion. The pathologist must be aware of the possible presence of spirochetes that can only be confirmed by a silver stain. The pathogenicity of spirochetosis remains to be defined.