C. Herpes Simplex Virus – This is not the correct answer

Image courtesy of Laura Blood, John Greene, MD, Albert Vincent, PhD, and Ramon Sandin, MD.

Herpes simplex virus (HSV) is in the same herpesvirdae family as VZV, and can be difficult to distinguish based simply on the presence of a “vesicular rash.” Both can appear in young healthy males and are sexually transmitted; both can cause secondary meningitis and can reactivate later in life. They can often be differentiated based on the location, distribution, and appearance of the rash.

Both herpes viruses have a primary and secondary phase that should be considered in this case. Primary HSV infection usually presents with multiple lesions in a local distribution, usually on oral mucosa (mouth and lips) (Figure). HSV reactivation primarily presents as painful vesicles or ulcers, single or multiple, again on the oral mucosa such as lips (vesicular “cold sores”), mouth (ulcers), and the genital region (vesicular lesions). Primary infection for VZV (ie, chickenpox) presents with a pruritic, disseminated, vesicular-pustular rash, with lesions at various stages of development. VZV reactivation, or zoster, classically presents on any body surface, skin or mucosa, but is limited to a unilateral dermatomal distribution. Both viruses are extremely contagious during their vesicular phase in both their primary and reactivation forms.

Direct fluorescent antibody testing and culture distinguished the two definitively in this case. HSV encephalitis is less likely in this case; it typically manifests with temporal-parietal involvement, altered mental status, increased blood and blood products in the CSF, and sometimes seizures. None of these features was present in this case.

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