A 33-year-old man presents to the emergency department with reports of anal and rectal pain, rectal bleeding, tenesmus, and mucus in his stools. The symptoms have become unrelenting. He has a family history of inflammatory bowel disease. He is in a heterosexual relationship and has not had sex with men. He has only a distant history of sexually transmitted diseases (gonorrhea, cured with ceftriaxone). He recently had a Campylobacter infection severe enough to be treated with azithromycin, which was resolved.

Initial blood work revealed a white blood cell count of 12.1 × 10^₉, lactate of 2.0 mmol/L, and C-reactive protein of 109 mg/L. The remainder of his blood work was within the normal limits. Testing for antineutrophil cytoplasmic antibodies and perinuclear anti-neutrophil cytoplasmic antibodies was negative, and stool culture and Clostridium difficile testing were negative.

Endoscopy revealed involvement at the dentate line, confinement to the rectum, a clear upper limit with the proximal mucosa appearing normal; diffuse and uniform involvement; granular, friable mucosa with blurring or absence of the normal vascular pattern; and spontaneous bleeding. The remainder of the colon and small intestine were normal.