Trigeminal Herpes Zoster With Mucosal Involvement in a Patient on Prophylactic Valacyclovir: An Uncommon Presentation.

This case report details a unique presentation of trigeminal herpes zoster with mucosal involvement in a 72-year-old female undergoing prophylactic valacyclovir treatment for suspected herpes labialis. The patient initially presented for a routine skin examination. Despite the absence of clinical evidence of herpes labialis, she was prescribed prophylactic valacyclovir. Three days later, the patient developed a unilateral rash, gingival darkening, and severe ipsilateral tooth pain. An examination revealed a crusted erythematous rash along the mandibular division of the left trigeminal nerve and a darkening of the gums. Diagnosed with trigeminal herpes zoster, she was treated with valacyclovir and a prednisone taper. A follow-up showed the resolution of the skin and gingival lesions, though herpetic neuralgia persisted. This case underscores the complexity and potential atypical presentations of herpes zoster, even under prophylactic antiviral therapy. It highlights the importance of considering herpes zoster in differential diagnoses, especially in patients presenting with unilateral dermatological and mucosal symptoms.