Zosteriform herpes simplex and herpes zoster: A clinical clue

Sir,

This is in response to the article, ‘Recurrence of zosteriform lesions on the contralateral dermatome: A diagnostic dilemma.’ by Udayashankar C et al.[1] They concluded that the patient had recurrence of zosteriform lesions on the left T4-5 dermatomes, of which T4 is the corresponding contralateral dermatome to the previous episode and had a diagnostic dilemma as they did not have the laboratory evidence for the causative organism, which could be either herpes simplex or varicella zoster virus.

We completely agree with the importance of identifying the causative organism as proper diagnosis will lead to more accurate therapy.[1] It is important to distinguish between these two viruses with the advent of antiviral drugs and isolation procedures.[2]

We would like to add a clinical clue, which could possibly help in differentiating between these two conditions. We would like to point out an important clinical observation by many authors that the vesicles of herpes simplex are uniform in size in contrast to the vesicles seen in herpes zoster, which vary in size.[3,4,5] In other words, vesicles of herpes simplex are uniform within a cluster.[3] A later recurrence proves the diagnosis of simplex.[4,6] Koh MJ et al. reported a 65-year-old man who presented with recurrent episodes of a “zosteriform eruption”. He was initially clinically diagnosed and treated for recurrent herpes zoster, but was subsequently found to have recurrent herpes simplex virus type 2 after laboratory investigations.[6]

With the above clinical clue it is more likely, from the clinical features and the photograph, that this was a case of zosteriform herpes simplex (uniform vesicles within a cluster).