Paraneoplastic or treatment-associated dermatomyositis: a diagnostic challenge.

Dermatomyositis (DM) is a systemic autoimmune disorder characterized by proximal myopathy and dermatological findings. Approximately 15-30% of DM cases emerge as a paraneoplastic syndrome caused by a concomitant malignancy. Although more rare, in cancer patients DM has also been reported as a possible result of toxicity of some antineoplastic agents, such as taxanes and monoclonal antibodies. Herein, we report a 35-year-old woman with metastatic breast cancer who presented with skin lesions after initiation of paclitaxel and anti-HER2 agents. Clinical, laboratory, and histological findings were consistent with the diagnosis of DM.