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Case Reports

Abstract

While talimogene laherparepvec (TVEC) is a known effective treatment for unresectable melanoma, it may cause adverse herpetic events, including in immunocompetent patients without prior HSV history. We present the case of a 47-year-old immunocompetent male with metastatic melanoma who had previously been treated with checkpoint inhibitors. After experiencing disease progression and side effect intolerance with pembrolizumab, ipilimumab, and nivolumab, he started TVEC therapy. Lesions were injected without immediate complication, but within 24 hours, he developed a pruritic rash along with fever, chills, myalgia, vomiting, diarrhea, and confusion. Clinical exam revealed deep dermal nodules on the left lower leg and scattered vesicles with an erythematous base. A shave biopsy revealed ballooning epithelial necrosis, extensive papillary dermal edema, and a mixed infiltrate of lymphocytes, neutrophils, and karyorrhectic debris, with underlying dermatoheliosis. These findings were consistent with HSV reactivation following TVEC injection. The patient was treated with a 10-day course of valacyclovir, resulting in complete resolution of his symptoms. This case highlights the importance of recognizing HSV reactivation following TVEC therapy, even in immunocompetent patients. Timely initiation of antiviral therapy is critical in preventing more serious complications. This case adds to the growing body of literature on TVEC-related adverse events and emphasizes the need for careful monitoring during treatment.