Case Report of Dermatomyositis With Features of the Wong Variant Developing Post‐Trastuzumab Therapy for Breast Cancer

Drug-induced dermatomyositis can be challenging to distinguish from paraneoplastic dermatomyositis. Rarely, antibodies directed against human epidermal growth factor receptor 2 (HER-2), such as trastuzumab, may trigger dermatomyositis, and immune checkpoint inhibitors may incite the Wong variant of dermatomyositis, characterised by clinical and histopathologic features of pityriasis rubra pilaris, including monomorphic keratotic papules. We present an unusual case of dermatomyositis with features of the Wong variant occurring in a 51-year-old female with a history of breast cancer after completion of adjuvant therapy with trastuzumab.