Abstract

Introduction

It has become increasingly important for dermatologists to recognize Mpox after the outbreak in 2022. Diagnosis from clinical features alone can be challenging given its morphological evolution. We describe the various clinical morphologies and the corresponding the histopathologic features and compare our findings with the reported literature.

Materials/Methods

We retrospectively reviewed six skin biopsies of confirmed Mpox infection in various stages of evolution which included papular, umbilicated plaque, crusted plaque, ulcer, and early/late pseudotumor. We examined and graded all specimens for the following features: epidermal keratinocyte pallor, ballooning degeneration, intraepidermal vesiculation, acantholysis, intranuclear inclusions, multinucleate keratinocytes, neutrophilic epitheliotropism, epidermal hyperplasia, perifollicular and/or adnexal infiltrate, dermal infiltrate (with predominant cell type), vascular changes, and degree of epidermal necrosis.

Findings

There were no distinguishing histopathologic features between the clinical stages. 4/6 cases demonstrated prominent necrosis involving the lower half the epidermis, along with prominent vascular changes ranging from endothelial swelling to vessel necrosis. Intranuclear eosinophilic inclusions, which have been previously described as a distinguishing feature from HSV or VZV infection, were readily detected in only 2/6 cases.

Discussion

Although our cases did not demonstrate stage dependent features, some important findings were noted. The marked necrosis in the lower half of the epidermis contrasts with atypical Coxsackievirus infection, which frequently demonstrates significant necrosis in the upper third of the epidermis. Significant acantholysis and intraepidermal vesiculation were lacking in our cases and those reported in the literature, which can potentially help distinguish Mpox from HSV and VZV infections.