An Unusual Case of Drug-Induced Hypersensitivity Syndrome With Multiple Atypical Histopathologic Findings.

Drug-induced hypersensitivity syndrome (DIHS) is a rare, severe cutaneous adverse reaction that presents with rash, fever, and multiorgan involvement after medication or supplement exposure. Diagnosis is primarily clinical, although a skin biopsy may provide supportive evidence. Histologic features vary but generally reflect nonspecific epidermal and dermal inflammatory patterns. Rarely, DIHS presents with atypical features such as pustules, imitating acute generalized exanthematous pustulosis. We describe a case of a 68-year-old man who was started on carbamazepine for postoperative seizures and subsequently presented with a diffuse morbilliform rash with pustular components and distributive shock. He also displayed fever, lymphadenopathy, eosinophilia, acute kidney injury, and hepatitis, leading to a diagnosis of DIHS. A biopsy revealed interface dermatitis with eosinophils, subcorneal neutrophilic pustules, and dermal granulomatous inflammation. Although DIHS displays a broad spectrum of histologic features, a granulomatous reaction has been rarely reported. Herein, we describe a case of DIHS with granulomatous features.