Multidermatomal Herpes Zoster Involving All Three Branches of the Trigeminal Nerve in an Immunocompetent Adult: A Case Report

Background and Clinical Significance: Herpes zoster (HZ), caused by the reactivation of the latent Varicella-Zoster virus (VZV), typically is confined to a single dermatome in immunocompetent individuals. Thus, multidermatomal involvement, particularly simultaneous reactivation across all three branches of the trigeminal nerve, is exceedingly rare without history of immunosuppression. Case Presentation: We present the case of a 60-year-old immunocompetent male who presented to the Emergency Department with a two-day history of a rapidly progressive, painful vesicular eruption over the entire left side of his face, including the intraoral mucosa. Clinical evaluation, polymerase chain reaction (PCR) and serology testing confirmed VZV reactivation across the V1, V2, and V3 dermatomes. Extensive diagnostic workup, including HIV serology and whole-body computed tomography, revealed no underlying immunodeficiency or occult malignancy. The patient was treated promptly with oral valacyclovir and topical ointments, resulting in rapid crusting and healing within one week without severe complications. Conclusions: This case highlights that multidermatomal trigeminal HZ can occur in healthy individuals and emphasizes the importance of prompt diagnostic workup and antiviral therapy to prevent devastating ocular and neurological sequelae.