A Challenging Case of Eyelid Ptosis and Diplopia Induced by Pembrolizumab.

We present the case of an 83-year-old female patient with gastric adenocarcinoma, who developed a subacute onset of eyelid ptosis and ophthalmoparesis, while being treated with pembrolizumab, raising the suspicion of myasthenia gravis. Workup exposed a broader systemic involvement, with liver, cardiac and skeletal muscle being affected as well. Further investigation lead us to change our initial diagnosis to multisystem inflammatory syndrome with isolated symptomatic ocular myositis, induced by pembrolizumab. High-dose steroids and immunoglobulin were started with a good outcome.