Exclusive involvement of folliculosebaceous units by herpes: a reflection of early herpes zoster.

The histopathological changes of herpes simplex, herpes zoster, and varicella are considered to be indistinguishable from one another. Evaluation of the clinical setting, with adjunctive studies if necessary, generally clarifies the specific diagnosis. Vesicular lesions in all three conditions can involve epidermal and adnexal epithelium with characteristic cytopathic features. We describe three patients with non-vesicular eruptions on the head and neck whose biopsies revealed exclusive folliculosebaceous involvement by herpes. All three patients developed typical herpes zoster within days of the biopsy. There is compelling scientific evidence in the literature indicating that, in herpes zoster, the virus is transported from dorsal root or trigeminal ganglia via myelinated nerves to the skin. These terminate at the isthmus of hair follicles and primary infection of follicular and sebaceous epithelium occurs. Spread of infection to the epidermis follows. In contrast, data pertaining to recurrent herpes simplex indicates that axonal transport of the virus from sensory ganglia to the skin is directed primarily to the epidermis, via terminal non-myelinated nerve twigs. The clinical evolution of our three cases and scientific data in the literature indicate that exclusive folliculosebaceous involvement by herpes, in the setting of a non-vesicular eruption, represents early herpes zoster.