Abstract
<h3>Objective:</h3> NA <h3>Background:</h3> Checkpoint inhibitor-induced myasthenia gravis is a life-threatening complication with mortality near 60%.<sup>1</sup> Two patients with pembrolizumab-induced myasthenia gravis responded favorably to efgartigimod. <h3>Design/Methods:</h3> NA <h3>Results:</h3> A 68-year-old female with metastatic gallbladder cancer developed ptosis, ophthalmoparesis, and weakness one month after receiving pembrolizumab. She has acetylcholine receptor (binding, blocking) and striated muscle antibodies without thymoma. Her ptosis improved with prednisone 20mg daily. She developed dysphagia, hoarseness, and gait instability which resolved with increased prednisone 60mg. Prednisone was tapered; proximal limb weakness and ptosis returned at 30mg. Efgartigimod improved symptoms after second infusion. Three weeks after cycle one while alternating prednisone 25mg–20mg, she developed exertional dyspnea, hoarseness, and worsening ptosis. Increased prednisone to 25mg. Her symptoms persisted; five weeks after cycle one, the second cycle of efgartigimod started and her symptoms nearly resolved, with intermittent ptosis. She is stable on prednisone 25mg with slow taper. A 78-year-old female with metastatic urothelial carcinoma status post two doses of pembrolizumab presented with dyspnea, leg weakness, and myalgias. She developed ptosis, ophthalmoparesis, and dysphagia. Acetylcholine receptor and MuSK antibodies were negative. Intravenous immunoglobulin was ineffective to prevent worsening. After the second dose, she developed respiratory failure requiring intubation. Prednisone 40mg BID and plasmapheresis (PLEX) were initiated. Her strength improved enough for extubation; subsequently aspirated and required reintubation. Rituximab was infused for long-term immunosuppression while another PLEX cycle was started. She developed thrombocytopenia and gastrointestinal bleeding; PLEX was discontinued after 3 doses. Efgartigimod initiation two days after the final PLEX infusion led to improved strength, ophthalmoparesis, and thrombocytopenia within one week. She died from urosepsis two days after the second dose. <h3>Conclusions:</h3> Current treatments for pembrolizumab-induced myasthenia gravis are corticosteroids, IVIG, and plasmapheresis. Rituximab is effective in refractory cases, although onset of action can take more than 6 weeks.<sup>2</sup> Efgartigimod rapidly improved myasthenia gravis symptoms in both patients. <b>Disclosure:</b> Miss Campbell has nothing to disclose. Dr. Rodriguez-Hernandez has nothing to disclose. Dr. Rizvi has nothing to disclose. Dr. Swerdloff has nothing to disclose. The institution of Dr. Zakin has received research support from American Board of Psychiatry and Neurology. Dr. Faktorovich has a non-compensated relationship as a Board of Directors with Brother’s Brother Foundation that is relevant to AAN interests or activities.
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