Abstract Intro Pembrolizumab is an immune checkpoint inhibitor (ICI) approved to treat several malignancies. Neurologic immune-related adverse events are seen in about 14% patients receiving ICI. However, myasthenia gravis (MG) is recognized as a rare event which can result in increased mortality from respiratory failure. We report the case of a pembrolizumab induced MG requiring intensive care unit (ICU) admission and non-invasive ventilatory therapy. Case A 72-year-old female with metastatic uterine cancer presented with sub-acute onset of diplopia. She recently completed 3rd cycle of pembrolizumab monotherapy in addition to her cytotoxic chemotherapy. A week before presentation, she noticed eyelid fatigue and inability to open her eyes. She was noted to be hypoxic and in respiratory distress on presentation. Physical examination revealed bilateral ptosis with marked esotropia and reduced upward gaze. She had neck weakness and bilateral deltoid weakness (power 4/5). Patient was placed on non-invasive ventilatory therapy and admitted to ICU. Imaging studies of the brain, chest and initial laboratory data were unremarkable. Due to suspicion for myasthenic crisis, patient was started on pyridostigmine and intravenous steroids. Electromyography results of deltoid muscle was consistent with MG. Patient was started on intravenous immunoglobulin (IVIG) therapy. An antibody panel revealed a positive titer for anti-acetylcholinesterase receptor (0.5 nmol/L) which was also consistent with the diagnosis of MG. Patient improved and was weaned off non-invasive ventilatory support. Her negative inspiratory force and vital capacity continued to improve. She was subsequently discharged with permanent cessation of pembrolizumab therapy. Discussion Few cases have reported describing pembrolizumab-induced MG in patients being treated for gynecologic malignancies. MG in such patients might be difficult to diagnose due to variability of symptoms, overlap with other neurologic conditions, paraneoplastic syndromes, lack of specificity on routine blood testing as well as imaging studies and lack of provider knowledge. There by, MG should be considered in the differential for patients presenting with pseudobulbar symptoms, new-onset/worsening limb weakness and undergoing therapy with ICI. Respiratory failure being the most common cause of mortality in such patients, negative inspiratory forces and vital capacity should be closely monitored. Patients should be closely monitored and might require ventilatory support. Treatment options include pyridostigmine, steroids, IVIG and plasmapheresis along with avoiding medications that can worsen MG. Conclusion Immune-checkpoint inhibitor therapy related MG is a rare but serious, potentially life threatening adverse event. Prompt diagnosis, close monitoring and rapid initiation of treatment is imperative in reducing morbidity and mortality. This abstract is funded by: None
Valiveti et al. (Fri,) studied this question.