New-Onset Graves' Ophthalmopathy After Treatment with Pembrolizumab: A Case Report and a Review of the Literature.

Immune checkpoint inhibitors (ICIs), a revolutionary class of oncology therapeutics that enhance T cell-mediated antitumor immunity, are associated with various immune-related adverse events (IRAEs). While destructive thyroiditis and hypothyroidism are common, ICI-induced Graves' disease (GD) is exceedingly rare, and the occurrence of concomitant Graves' ophthalmopathy (GO) is even rarer. A 57-year-old man with bladder cancer developed GO after receiving the first dose of the programmed death 1 (PD-1) inhibitor pembrolizumab. He presented with severe proptosis, extraocular muscle enlargement, hyperthyroidism, and significantly increased thyroid-stimulating hormone receptor autoantibodies (TRAb). Following the treatment with glucocorticoids and immunosuppressive therapy, his symptoms improved markedly but relapsed upon dosage reduction. To date, we have not identified any previous reports of GO with confirmed positive thyroid-related antibodies induced by pembrolizumab. This case offers valuable insights into the potential IRAEs, underscoring the importance of thorough clinical evaluation and early recognition to improve patient outcomes and quality of life. A literature review of ICI-induced GO was also performed, with further discussion of the potential pathogenic mechanisms, risk factors, and management strategies.