Pembrolizumab-associated choroidal inflammation on a background of treated choroidal melanoma

We report a rare case of isolated choroidal inflammation in a patient with a history of treated choroidal melanoma who subsequently developed cutaneous melanoma and underwent adjuvant treatment with pembrolizumab. The patient presented with a new choroidal lesion adjacent to the treated choroidal melanoma. Differential diagnosis included recurrence of choroidal melanoma, metastases from the cutaneous melanoma or pembrolizumab-associated choroidal inflammation. Ultrasound findings suggested an inflammatory aetiology and the patient was treated with an intravitreal dexamethasone implant. One month later, the lesion had regressed and visual acuity improved. Pembrolizumab, an immune checkpoint inhibitor, can cause ocular immune-related adverse effects, including choroidal inflammation. This case underscores the importance of distinguishing between inflammatory and metastatic lesions, particularly in patients with a history of ocular malignancy. Early recognition and appropriate treatment with steroids can prevent irreversible vision loss and multimodal imaging is crucial in such cases.