Long-term adverse event: inflammatory orbitopathy induced by pembrolizumab in a patient with metastatic melanoma

The recent advent of immune checkpoint inhibitors (ICI), including anti-programmed cell death 1 protein (anti-PD-1) agents has revolutionized the therapeutic approach of metastatic malignancies. Yet, ICI can disrupt immune tolerance resulting in enhanced immune activation in normal tissues with significant toxicity. A dysregulated activation of T-cells directed to normal tissues stands as the main mechanism of immune-related adverse events (irAE). To date, only two cases of immune-related inflammatory orbitopathy related to anti-PD-1 agents have been reported. This rare immune adverse event usually occurred early after ICI initiation. Here, we report the first case of late inflammatory orbitopathy occurring in a melanoma patient treated with pembrolizumab. Consequently, the occurrence of irAE under ICI should be monitored, even late after treatment instauration.