# Reactivation of Herpes Zoster in a Young Patient With Multiple Sclerosis Under Dimethyl Fumarate Treatment and Normal Lymphocyte Subsets Count: A Case Report

## TL;DR

A young multiple sclerosis patient on dimethyl fumarate developed herpes zoster despite normal lymphocyte levels, highlighting potential infection risks.

## Contribution

This case report is the first to describe HZ reactivation in an MS patient on DMF with normal lymphocyte counts.

## Key findings

- A 26-year-old MS patient on DMF developed herpes zoster with normal absolute lymphocyte count.
- The case suggests a need for increased awareness of infection risks in MS patients treated with DMF.
- Immunization against VZV may be beneficial for DMF recipients.

## Abstract

Herpes zoster (HZ) infection results from the reactivation of the varicella-zoster virus (VZV), which remains dormant in the dorsal root ganglia after an initial chickenpox infection. Although HZ appears more common in people with multiple sclerosis (MS) than expected in the general population, few studies have investigated this association, particularly with a normal absolute lymphocyte count (ALC). Additionally, no reported cases have discussed the clinical presentation of such patients. This report describes the case of a 26-year-old female with a known history of relapsing-remitting MS on dimethyl fumarate (DMF) treatment. She presented with a history of painful erythematous blisters, diagnosed as acute HZ infection with a normal ALC. This case provides evidence that warrants further research and attention to the management of patients with MS receiving DMF, particularly regarding infectious risks. It highlights the importance of pharmacovigilance and the potential benefits of VZV and HZ immunization in DMF recipients.