Nivolumab-induced Lambert-Eaton myasthenic syndrome: an immune-related adverse event in nonsmall cell lung cancer.

Nivolumab is an anti-programmed cell death protein 1 (anti-PD-1) monoclonal antibody and was the first immune checkpoint inhibitor drug approved for use in advanced non-small cell lung cancer (NSCLC). In this report, we describe a rare case of Lambert-Eaton myasthenic syndrome (LEMS), which developed as a side effect of nivolumab in a patient with metastatic lung squamous cell carcinoma. Our patient, who was previously treated with nivolumab for metastatic squamous cell carcinoma of the lung, appeared with a headache, swollen face, dysarthria, asthenia, xerostomia, and drooping eyelid.