Immune checkpoint inhibitor lichenoid eruption due to pembrolizumab

Pembrolizumab is an immune checkpoint inhibitor used in many cancer types, including genitourinary cancers. Although immunotherapies have dramatically changed the landscape of cancer treatment by providing an alternative to traditional chemotherapy, they have been associated with significant immune-related adverse events (IRAEs) with wide-ranging clinical manifestations. We present the case of an elderly woman on pembrolizumab for metastatic bladder cancer who developed cutaneous IRAE with lichenoid eruptions that responded to high-dose intravenous glucocorticoids.