Fatal triad of checkpoint inhibitors: Pembrolizumab induced myasthenia gravis with myositis and myocarditis in a patient with thymoma

Abstract

Pembrolizumab is an immune checkpoint inhibitor that acts by blocking programmed cell death proteins, however, its use is limited in patients with thymoma. We describe a 31-year-old woman with thymoma who developed myocarditis, myositis and exacerbation of myasthenia gravis due to use of pembrolizumab. There were elevations of creatine phosphokinase, troponin T, CK-MB, alanine aminotransferase, aspartate aminotransferase and lactate dehydrogenase. Electrophysiologic studies showed a myopathic pattern and more than 10% decremental response on repetitive nerve stimulation. Steroid and intravenous immunoglobulin treatment was initiated. Because of a lack of improvement she received 5 cycles of plasma exchange. The patient benefited significantly from plasmapheresis and was discharged with noninvasive mechanical ventilation after one hundred and fifteen days of hospitalization. Plasmapheresis in the early period can be an effective treatment option in patients who develop severe neurological symptom with use of checkpoint inhibitors.