Enfortumab vedotin-induced widespread vesiculobullous eruption mimicking disseminated herpetic infection in a patient with metastatic urothelial carcinoma

Enfortumab vedotin (EV) is a monoclonal antibody drug conjugate composed of antibody against nectin-4 and linked to the microtubule inhibitor monomethyl auristatin E that is used to treat metastatic urothelial carcinoma. Enfortumab vedotin-associated cutaneous adverse events are common and are clinically diverse, ranging from papulosquamous eruption to vesiculobullous eruptions such as Stevens-Johnson syndrome/toxic epidermal necrolysis and erythema multiforme-like eruption with vesiculobullae. Despite clinically diverse appearance, histopathology of EV-associated cutaneous adverse reactions often demonstrates interface dermatitis. We present the clinical and histopathologic features in a unique case of EV-associated widespread vesiculobullous eruption initially concerning for disseminated herpetic infection in a patient undergoing treatment of metastatic urothelial carcinoma with EV and pembrolizumab.