New Onset Ocular Myasthenia Gravis After Pembrolizumab Therapy: a Case Report

Abstract

Immunotherapy is the most recent and promising discovery in the treatment of advanced cancers resistant to conventional chemotherapy. Pembrolizumab is an immune checkpoint inhibitor that was recently approved for treatment of nonsmall cell lung carcinoma. Similar to other immune checkpoint inhibitors, its exact toxicity profile is still unknown. Neurologic immune-related adverse events from use of immune checkpoint inhibitors are rare with an incidence of only less than 4%. Severe adverse events including myasthenia gravis have only been reported in less than 1% of cases. We report a rare case of new onset ocular myasthenia gravis in a patient with advanced nonsmall cell lung carcinoma who became symptomatic after 4 cycles of Pembrolizumab. The diagnosis was established by clinical history, compatible single fiber electromyography findings, and initial response with oral Pyridostigmine. Resolution of neurologic symptoms was achieved after discontinuation of pembrolizumab and treatment with oral Pyridostigmine. As the use of immunotherapy is becoming more available and widely accepted, it is imperative to have a high index of suspicion for neurologic immune-related adverse events. Early detection and prompt treatment of these adverse events can reduce long-term morbidity and mortality.