Rhabdomyolysis following single administration of pembrolizumab: Is severe immune-reaction a marker for durable treatment response?

• Immune checkpoint inhibitors are approved for all mismatch repair deficient tumors. • Although rare, autoimmune myositis complicating pembrolizumab therapy may be fatal. • In this case, pembrolizumab caused rhabdomyolysis but also a durable response. • Severe autoimmune reaction may be associated with durable treatment response.