Intestinal Spirochetosis: A Cause of Symptoms Resembling Irritable Bowel Syndrome

Abstract

Purpose: Intestinal spirochetosis (IS) is an uncommon, but treatable cause of gastrointestinal symptoms that often resemble irritable bowel syndrome (IBS). We report a case of IS in a homosexual male presenting with chronic watery diarrhea. A 25 year old homosexual male of Asian origin presented with an eight-year history of watery diarrhea. He denied rectal bleeding, abdominal pain and weight loss. Physical examination was unremarkable. Biochemical and hematological parameters were normal. Stool examination did not reveal conventional pathogens. No gross abnormalities were noted on colonoscopy. Hematoxylin and eosin (H &E) stained slides of colonic mucosal biopsy specimens revealed a focally prominent surface epithelial brush border with basophilic microorganisms adherent to the epithelial surface, suggestive of IS. The diagnosis was confirmed with Steiner silver stain, which highlighted surface microorganisms. A seven day course of oral metronidazole was offered as therapy for IS. IS is an uncommon clinical entity in North America, with an estimated prevalence of 2.5% to 6.5%. Higher prevalence rates (11.4 to 64.3%) have been observed in developing countries, in homosexuals and HIV-infected individuals. Colonization of the colonic mucosa by various species of spirochetes, including Brachyspira aalborgi and Serpulina pilosicoli, is almost an incidental finding in an asymptomatic patient. Spirochetal invasion of the colonic epithelium, resulting in epithelial changes and inflammatory infiltrate in the lamina propria, is associated with symptoms. However, in homosexual men, regardless of HIV status, symptoms may be present in the absence of epithelial invasion. Persistent diarrhea, abdominal pain or constipation occur either alone or in combination, often resembling IBS. The diagnosis of IS is suspected on H & E staining of colonic mucosal specimens, and confirmed by silver stains, immunohistochemistry or electron microscopy. Due to patchy distribution of spirochetes, multiple site colonic biopsies are recommended for a definitive diagnosis. Of the several regimens proposed, metronidazole seems to be superior in eradicating spirochetes from the intestine. In conclusion, IS should be considered as a differential diagnosis in patients with IBS-like symptoms, with an otherwise grossly normal-appearing colonic mucosa. Metronidazole should be offered as first-line therapy for the treatment of IS.