# Human Herpesvirus 6-Associated Miller–Fisher Syndrome in a 5-Year-Old Child: A Case-Based Narrative Review of Pediatric Cases with Infectious Triggers

## TL;DR

A 5-year-old child with Miller–Fisher syndrome (MFS) showed evidence of human herpesvirus 6 (HHV-6) in cerebrospinal fluid, suggesting a possible infectious trigger for this rare neurological condition in children.

## Contribution

This is the first reported case linking HHV-6 to pediatric MFS and a review of 20 pediatric cases showing infectious triggers and treatment outcomes.

## Key findings

- HHV-6 DNA was detected in cerebrospinal fluid of a child with MFS, with no other pathogens identified.
- Among 20 pediatric MFS cases reviewed, Campylobacter jejuni was the most common infectious trigger, followed by Mycoplasma pneumoniae and influenza.
- Most pediatric MFS cases responded well to immunotherapy and had favorable outcomes, even when managed conservatively.

## Abstract

Background/Objectives: Miller–Fisher syndrome (MFS) is a rare Guillain–Barré variant defined by ophthalmoplegia, ataxia, and areflexia. Pediatric MFS is uncommon, and infectious triggers remain underrecognized. Human herpesvirus 6 (HHV-6) is neurotropic but rarely linked to immune-mediated neuropathies. In this paper, we describe a child with MFS associated with HHV-6 detected in cerebrospinal fluid (CSF) and review reported pediatric infections related to MFS. Methods: A 5-year-old girl presented with acute ophthalmoplegia, ataxia, and diminished reflexes. Neuroimaging, ophthalmologic tests, CSF analyses, and serologic andpolymerase chain reaction (PCR) assays were performed, including multiplex reverse transcription–PCR of cerebrospinal fluid using the BioFire® Meningitis/Encephalitis panel. A literature search was performed on Pubmed to identify pediatric (0–18 years) MFS cases with infectious triggers. Two reviewers independently screened and summarized the literature, and a PRISMA-style flow diagram was used to transparently report the study selection process. Results: HHV-6 DNA was detected via CSF PCR twice, while tests for other pathogens were negative. Anti-GQ1b and related antibodies were negative or borderline. The patient received intravenous immunoglobulin and corticosteroids, with full recovery after one month. Among 20 published pediatric cases (1997–2021), Campylobacter jejuni was most frequent, followed by Mycoplasma pneumoniae and influenza viruses. Anti-GQ1b IgM positivity and favorable outcomes were commonly reported, including cases managed conservatively. Conclusions: This case raises the hypothesis that HHV-6 may represent a potential post-infectious association in pediatric MFS. The review findings indicate that pediatric MFS generally follows infection, responds well to immunotherapy, and has an excellent prognosis. Viral testing may be considered in selected, hypothesis-generating contexts in atypical or seronegative pediatric MFS presentations.