Severe Mpox-Associated Proctocolitis Mimicking Opportunistic Colitis in a Liver Transplant Recipient.

Mpox infection increasingly manifests with anorectal disease during the recent global outbreak. Severe ulcerative proctocolitis in solid-organ transplant recipients remains rarely described. We report a 37-year-old liver transplant recipient with well-controlled HIV infection (CD4 count 661 cells/µL [35%] and HIV RNA <20 copies/mL) presenting with severe watery diarrhea, rectal pain, disseminated vesiculopustular lesions, and inflammatory proctocolitis on imaging and endoscopy. Histopathology demonstrated ulceration and cryptitis without viral inclusions, while extensive infectious evaluation was negative. Polymerase chain reaction testing of a cutaneous lesion was positive for mpox virus. Symptoms improved with supportive care and reduction of immunosuppression. This case highlights mpox as an important diagnostic consideration in immunocompromised patients presenting with severe ulcerative proctocolitis, including patients with preserved CD4 immunity and virologically suppressed HIV infection.