Exacerbation of myasthenia gravis in a patient with melanoma treated with pembrolizumab

Introduction: While anticancer immunotherapies have traditionally focused on activation of the immune system, there is recent interest in disinhibition of the natural antitumor immune response by targeting immune checkpoints such as cytotoxic T-lymphocyte associated antigen-4 (CTLA-4) and programmed death-1 (PD-1). One humanized monoclonal antibody against PD-1, pembrolizumab, was recently approved for treatment of metastatic malignant melanoma. Methods: We report exacerbation of myasthenia gravis (MG) after treatment with pembrolizumab and provide a brief literature review. Results: We describe a 75-year-old man with stable MG who experienced myasthenic crisis in the setting of pembrolizumab treatment. A concurrent azathioprine taper was a possible although unlikely contributor given the short time interval between taper and exacerbation. Conclusions: As long-term data become available regarding the adverse immune effects of novel checkpoint inhibitors, clinicians should be mindful of their risks/benefits and of possible autoimmune disease exacerbation. Muscle Nerve54: 157-161, 2016