Pembrolizumab Therapy Triggering an Exacerbation of Preexisting Autoimmune Disease

Historically, metastatic melanoma was uniformly and rapidly lethal, and treatment options were limited. In recent years, however, checkpoint inhibitors have emerged as an accepted standard treatment for patients with advanced melanoma. In clinical trials, these agents have been largely well tolerated and have the potential to result in durable responses. Importantly though, one must recognize the unique side effect profile of these therapies, which can trigger or exacerbate underlying autoimmune disease. Whether this autoimmune activation is associated with a clinical response to therapy has been debated, and while not definitive, there is evidence in the literature of a possible association. The 2 cases presented describe this autoimmune phenomenon, along with a review of the existing literature on the relationship between response to immunotherapy and autoimmune side effects.