Shingle-minded: A Case of Vaccine-strain Varicella-zoster Meningoencephalitis in an Immunocompetent Child

Introduction: While the varicella zoster virus (VZV) vaccine is generally safe, it is a live attenuated virus with potential for reactivation and complications in immunocompetent and immunocompromised hosts.

Case Description: A fully immunized 10-year-old male with ADHD presented to a pediatric emergency department (ED) with headache and rash. Symptoms started five days prior to presentation with left upper extremity (LUE) pain, followed by the appearance of multiple blisters on the LUE. His pediatrician diagnosed him with shingles and recommended supportive care. The rash worsened and he developed severe frontal headache. In the ED, his temperature was 38.1ᵒ C. All other vitals were normal. Exam revealed LUE coalescing vesicles on an erythematous base, particularly in the C7 dermatome. Additional solitary lesions were noted on the left thigh and bilateral scapulae. While in the ED, he became confused, mistaking providers for school classmates. Head CT was unremarkable. Cerebral spinal fluid (CSF) revealed lymphocytosis (red blood cells 4, white blood cells 26, 82% lymphocytes, glucose 53, protein 32). Ultimately, LUE vesicles and CSF were VZV PCR positive. Genotyping showed vaccine-strain VZV (vVZV) rather than wild-type (wtVZV). He was diagnosed with vVZV meningoencephalitis. Initial immune workup was normal, including total IgG and subclasses, varicella IgG, HIV, and pneumococcal titers. The patient completed a 10-day course of intravenous acyclovir and a 14-day course of oral acyclovir. At 4-month follow-up, he was asymptomatic.

Discussion: VZV vaccine has an excellent safety profile, with a serious complication (i.e. zoster, meningitis) rate of only 2.6/100,000 doses. While the pathogenesis of vVZV meningitis remains unproven, it is hypothesized that vaccine-administered virus travels via sensory nerves to dorsal root ganglia. After a latency period, it reactivates, traveling first anterograde to the skin, presenting as zoster in a dermatome near the initial vaccination site, and then along the spinothalamic tract to the brain, causing meningitis. Since 2006, a two-dose VZV vaccine series has been recommended, to both increase efficacy and decrease vVZV reactivation. To date, this is only the fourth reported case of vVZV meningitis, and first case of encephalitis, in an immunocompetent host who completed the two-dose series. Interestingly, our patient is the only one with cervical, rather than thoracolumbar, zoster dermatomal distribution. Given that his initial VZV vaccine was administered in Puerto Rico, with the site undocumented, it may have been administered in the deltoid, rather than the anterolateral thigh, as is currently recommended.

Conclusion: Although infrequent, meningitis is a potential complication of VZV vaccination, even in immunocompetent hosts. This case is unique in the cervical zoster distribution, prepubertal presentation, and encephalopathic features rather than headache alone. We hope this case report encourages physicians to have a low threshold for lumbar puncture in patients with zoster and neurologic symptoms, regardless of immunization status or immunocompetency.