Endoscopic and Histologic Assessment of Monkey Pox–associated Proctitis

A 34-year-old man with history of HIV on antiretroviral therapy was admitted with skin rash and 2 weeks of rectal pain and bleeding. He reported anoreceptive intercourse with a male partner 3 weeks prior. His most recent CD4 count from 6 weeks prior was 693 cells/mm³. Physical examination revealed papular lesions on his face, trunk, arms, and buttocks (Figure A). He had no perianal lesions but experienced exquisite tenderness with digital rectal examination. Computed tomography of the pelvis demonstrated rectal wall thickening with perirectal fat stranding and reactive lymphadenopathy. The skin lesions were positive for monkey pox (MP) by polymerase chain reaction. Flexible sigmoidoscopy demonstrated erosions in the distal sigmoid colon and severe proctitis, characterized by deep ulceration and scattered pustular lesions (Figure B). Rectal biopsies revealed ulcerated mucosa with viral cytopathic effect, including multinucleation, nuclear clearing, chromatin margination, and multiple intranuclear inclusions (Figure C), similar to the findings of MP-infected skin lesions reported in the literature. Immunohistochemical studies for herpes simplex virus and cytomegalovirus were negative. Polymerase chain reaction for MP from the rectosigmoid cytology brush was positive, supporting a diagnosis of MP proctitis. The patient was treated with tecovirimat for 14 days with clinical improvement of skin lesions and anorectal symptoms.

MP-associated proctitis is an emerging important differential diagnosis as the current outbreak continues to unfold. Although rectal involvement is not uncommon, it has not been well-documented endoscopically and histologically. Here we report the endoscopic and histologic findings of this disease.