Human intestinal spirochetosis in an immunocompromised host: evaluation of eradication therapy by endoscopy, histopathology and bacteriology.

Human intestinal spirochetosis (HIS) is a colorectal infectious disease caused by Brachyspira species. We describe HIS in an immunocompromised, 62-year-old Japanese man who presented at Jichi Medical University Hospital with symptoms of diarrhea and bloody stool. He had rheumatoid arthritis that had been treated with immunosuppressive drugs for 10 years. Colonoscopy revealed multiple erythematous spots in the cecum and colon. A histopathological examination identified intestinal colonization by spirochetes, and Brachyspira pilosicoli was isolated from biopsy specimens, indicating a diagnosis of HIS. Metronidazole eradicated the spirochetes, the intestinal mucosa recovered to normal, and the clinical symptoms disappeared. This case suggests that it is important to keep in mind HIS in the differential diagnosis of immunocompromised patients with chronic diarrhea and bloody stool.