Abstract
Intestinal spirochetosis (IS) in humans is characterized by spirochetal microorganisms attached to the luminal surface of the colonic epithelium. In the present case, attached organisms appeared as 3- to 4 μm-thick (average thickness, 3.4 μm) basophilic fringes or haze in HE-stained endoscopic biopsy specimens. The basophilic fringes were clearly labeled by Treponema pallidum antiserum. Because IS is relatively rare in developed countries, thin basophilic fringes characteristic of IS are readily overlooked. Thus, the recognition of histological characteristics of this disease is important for its diagnosis.