Herpes Zoster in a 10 year-old

The patient is an otherwise healthy ten year-old boy with a two day history of grouped zosteriform vesicles on the left arm, anterior shoulder and upper back.  He has mild discomfort.  No known illnesses and on no medication.  He had two immunizations for varicella at the approopriate ages.

Observation:  All of the grouped vesicles appeared to be of uniform size.

Lab:  A Tzanck smear was positive for multinucleated giant cells.

Diagnosis:  Herpes zoster roughly C3 - 6.

Herpes zoster in children is unusual but not all that rare.  There are a few cases of HZ after vaccination for varicella.  As he felt well, and as the effect of specific antiviral therapy is not striking; after discussion with his mother it was elected to simply follow.  In out opinion, in healthy children and young adults the course of HZ is usually relatively mild and almost never followed by post-herpetic neuralgia.  Immunity seems to wear off over time and it appears that this attenuated vaccine is capable of causing H.Z.  The other possibility is that this is zosteriform simplex.  We did not culture for that. 
While researching this case, we looked up "zosteriform simplex."  An observation (ref 4) indicates that in these patients the vesicles are of uniform size (as we see here).  This would tilt us towards a diagnosis of Zosteriform Herpes Simplex here, and not of vaccine failure.  Should this child get a recurrence, that would clinch the diagnosis.

Reference:
1. Herpes zoster in children.

Peterson N, Goodman S, Peterson M. Cutis. 2016 Aug;98(2):94-5.

Abstract: Herpes zoster (HZ) in immunocompetent children is quite uncommon. Initial exposure to the varicella-zoster virus (VZV) may be from a wild-type or vaccine-related strain. Either strain may cause a latent infection and subsequent eruption of HZ. We present a case of HZ in a 15-month-old boy after receiving the varicella vaccination at 12 months of age. A review of the literature regarding the incidence, clinical characteristics, and diagnosis of HZ in children also is provided.

 

2. Herpes zoster and zosteriform herpes simplex virus infections in immunocompetent adults.

Kalman CM, Laskin OL. Am J Med. 1986 Nov;81(5):775-8.

Abstract: Among 111 immunocompetent patients referred to a general hospital setting with the clinical diagnosis of herpes zoster, viral cultures were obtained from 47 patients. Six of these patients (13 percent) had herpes simplex virus isolated, with four of the six infections involving the facial distribution, and the other two involving the T4 (breast) distribution. Excluding those in whom herpes simplex virus was isolated, the mean age (+/- SD) of the remaining 105 patients was 50 +/- 19 years. Thirty-two percent of the patients were at least 65 years old; however, 39 percent were younger than 40 years of age. Thus, herpes zoster frequently occurs in young, immunocompetent adults. Also, since zosteriform rashes may be caused by herpes simplex virus, viral cultures of lesions are useful to differentiate infections caused by herpes simplex virus from those due to varicella-zoster virus. The need to distinguish between these two viruses may be important with the advent of antiviral drugs and for use of the proper epidemiologic isolation procedures.

3. Varicella Vaccine (Wiki)
Vaccines are less effective among high-risk patients, as well as being more dangerous because they contain attenuated live virus. In a study performed on children with an impaired immune system, 30% had lost the antibody after five years, and 8% had already caught wild chickenpox in that five-year period.

4. Zosteriform herpes simplex and herpes zoster: A clinical clue

Sanath Aithal, Sheela Kuruvila, and Satyaki Ganguly. Indian Dermatol Online J. 2013 Oct-Dec; 4(4): 369.  Free Full Text.

Excerpt: 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. In other words, vesicles of herpes simplex are uniform within a cluster.