Herpes simplex virus is a double-stranded enveloped DNA virus, divided into serotypes HSV-1 and HSV-2. It is transmitted via contact with active lesions but may also occur in the latent phase due to subclinical virus shedding. HSV-1 typically infects the oropharynx, and HSV-2 the genital mucosa and skin (vulva > vagina > cervix), though each may also infect the other site. Active lesions appear as red papules, progressing to vesicles and coalescing into painful ulcers, and may be associated with systemic symptoms of fever, malaise, and tender inguinal lymph nodes. The virus migrates to the regional lumbosacral nerve ganglia, establishing a latent infection, and reactivates with immune depression. Neonatal HSV can be acquired during delivery if lesions are present and may be associated with localized or disseminated disease, with high mortality and morbidity.

Histologically, the lesions show ulcerated/ blistering epidermis with intracellular ballooning and reticular degeneration of keratinocytes and prominent acute inflammation. On cytology, squamous cells with HSV cytopathic effect are multinucleated with nuclear molding, eosinophilic (Cowdry A) to basophilic intranuclear viral inclusions and a “ground-glass” appearance.