Mpox: A case of subtle inclusions

Summary: A 53-year-old male with well controlled HIV presented to the hospital with fevers, chills, headaches, myalgia and a subtle vesicular eruption on the trunk and extremities. Patient also had a painful bulla at the anal verge. Patient denied any sick contacts or tick exposures, but did note receptive anal intercourse with a previous partner in the past month. Lumbar puncture was negative for infectious encephalopathy panel and swab of perianal lesion was negative for HSV and VZV. Patient was empirically treated with valacyclovir and benzoyl peroxide wash for presumed folliculitis. 4 mm punch biopsy of the perianal lesion was performed and consistent with abscess with pseudoepitheliomatous hyperplasia. PAS, GMS, Fite, Gram, Spirochete, CMV, and HSV stains were negative for infectious organisms. Shortly after pathology was read out, patient’s mpox PCR from the perianal lesion returned positive. On re-review of the pathology, focal eosinophilic cytoplasmic inclusions of keratinocytes were identified below the ulcerated epidermis, compatible with mpox. Patient’s mpox infection was managed symptomatically through the county health department. Patient did not receive the mpox vaccine as it was thought that his exposure was more than 14 days prior to diagnosis, and he was improving with supportive care.