Stevens-Johnson syndrome/toxic epidermal necrolysis as the initial presentation of paraneoplastic anti-TIF1-γ dermatomyositis.

We report a rare case of Stevens-Johnson syndrome/toxic epidermal necrolysis as the initial manifestation of paraneoplastic dermatomyositis in a 50-year-old man subsequently diagnosed with diffuse large B cell lymphoma, in the absence of any identifiable drug exposure. The patient presented with periorbital edema, progressive dusky blistering eruption (Nikolsky sign positive), mucositis, and histopathology consistent with Stevens-Johnson syndrome/toxic epidermal necrolysis. Over the following weeks, he developed proximal muscle weakness, elevated creatine kinase, and cutaneous signs of dermatomyositis, including heliotrope rash and Gottron's papules, with serologic confirmation via anti-TIF1-γ antibodies. Imaging revealed a hypermetabolic axillary mass, and excisional biopsy confirmed diffuse large B cell lymphoma. This case highlights a novel presentation of Stevens-Johnson syndrome/toxic epidermal necrolysis in the setting of autoimmune and paraneoplastic immune dysregulation. It underscores the importance of considering nondrug-induced triggers in Stevens-Johnson syndrome/toxic epidermal necrolysis.