Human Intestinal Spirochetosis as a Cause of Chronic Diarrhea in an Immunocompetent Patient: A Case Report

Human intestinal spirochetosis (HIS), commonly due to <i>Brachyspira aalborgi</i> or <i>Brachyspira pilosicoli</i> infection, represents the adhesion and colonization of spirochetes to the apical membrane of colonic and rectal epithelial cells. The clinical spectrum can range from asymptomatic to chronic watery diarrhea, abdominal pain, and, in rare cases, rectal bleeding. However, symptomatic cases are usually found in immunocompromised patients. It has been reported to have a high prevalence of human immunodeficiency virus (HIV) infection among homosexual men, cancer patients, and immunotherapy patients. It is also associated with irritable bowel syndrome, eosinophilic enterocolitis, possible colonic polyps, notable sessile serrated adenoma/polyp, and colon cancer. In this case report, an immunocompetent patient without risk factors presented with chronic watery diarrhea and unintentional weight loss of 3.18 kilograms after two months (body weight baseline was 74.5 kilograms, 4% of weight loss in two months). HIS was confirmed by biopsy through colonoscopy. The patient was treated with a 10-day course of metronidazole (500 mg, three times a day) with complete remission of diarrhea. Therefore, our study supports the necessity of considering HIS as part of the differential diagnosis for immunocompetent patients with chronic diarrhea and weight loss, despite risk factors.