Drug-Associated Dermatomyositis Following Ipilimumab Therapy: A Novel Immune-Mediated Adverse Event Associated With Cytotoxic T-Lymphocyte Antigen 4 Blockade

Importance Ipilimumab, a human monoclonal antibody targeted against cytotoxic T-lymphocyte antigen 4, has shown promise in the treatment of metastatic melanoma. However, given its mechanism of action, immune-related adverse effects have been reported with this therapy. Despite increasing reports of immune-related adverse effects related to ipilimumab therapy, dermatomyositis associated with this agent has not previously been reported. Observations We describe a woman undergoing treatment with ipilimumab for metastatic melanoma who developed classic cutaneous findings of dermatomyositis along with proximal muscle weakness and elevated muscle enzymes. Conclusions and Relevance This case adds to the expanding literature regarding immune-related adverse events associated with ipilimumab. To our knowledge, drug-induced dermatomyositis from ipilimumab has not previously been reported. Physicians should be aware of these potential immune-related adverse events and consider drug-associated dermatomyositis in the differential diagnosis in patients receiving ipilimumab who present with a cutaneous eruption or muscle weakness.