A 22-year-old male began with up to 12 loose stools per day, with mucus and no blood. They were present for two months, even during the night. Moreover, he complained of abdominal pain and weight loss. There were no findings on the blood tests. Fecal calprotectin was 225 μg/g. Stool microbiology tests were negative. Ileocolonoscopy displayed normal mucosa but the histological study of the biopsies showed Treponemas genus Brachispira. The patient had a sexual risk behavior. Treatment with metronidazole was initiated with clinical improvement.