Abstract

Prior to 2022, Mpox was a disease of predominantly Central and West Africa, with few reports of histopathologic findings. The recent outbreak in the USA led to many immunosuppressed patients receiving the 2 dose JYNNEOS vaccine. A 39-year-old male with HIV and a CD4 count less than 20 developed multiple large verrucous nodules after his first dose of the JYNNEOS Mpox vaccine. He subsequently developed multiple secondary infections of his lungs and joints and was treated with several courses of antibiotics, IV cidofovir, vaccinia IVIG, and both IV and oral tecovirimat. In view of the enlarging and recurrent cutaneous nodules on his face, palms, and soles, he received intralesional cidofovir injections, with improvement in lesion size.  Skin biopsy and histopathology demonstrated verrucous features of epidermal papillomatous and portions of the epidermis with hypergranulosis. In addition, epidermal ulceration and eosinophilic inclusions in keratinocytes were present, suggestive of a viral cytopathic effect. The dermis displayed a moderate to dense, mixed inflammatory infiltrate with numerous plasma cells and scattered eosinophils. Although, histopathologic findings of Mpox are not diagnostically specific, differentiation from other pox viruses, HSV, and treponema pallidum, immunohistochemistry and Mpox PCR testing can be utilized, as was the case in this patient. With an increase in Mpox cases globally and the increasing frequency of vaccination of the immunosuppressed population, providers should be aware of the potential risk of live virus transformation in immunosuppressed patients and dermatopathologists should be able to recognize these unique yet nonspecific histopathologic findings.