Paraneoplastic dermatomyositis and Stevens-Johnson syndrome related to immunotherapy.

Paraneoplastic syndromes such as dermatomyositis, often emerge as the initial clinical manifestation across various cancer types and are characterized by the development of B-cell responses targeting cancer-cell antigens that cross-react with normal skin and muscle cells. While these syndromes may alleviate following antineoplastic intervention, their response to immunotherapy remains elusive due to the exclusion of patients with autoimmune phenomena from clinical trials. In this report, we present the case of a female patient with advanced urothelial cancer presenting with dermatomyositis, who subsequently underwent treatment with anti-PD1 immunotherapy and experienced the onset of Stevens-Johnson syndrome. We discuss these two autoimmune entities and provide a comprehensive review of the existing literature to elucidate similar associations.