A Case of Pembrolizumab-Induced Myasthenia Gravis

Document Type

Conference Proceeding - Restricted Access

Publication Date

5-9-2025

Abstract

Immune-based therapies have revolutionized cancer treatment in the recent past, both by providing many new targets for therapy and by more specifically targeting cancer cells, thereby significantly reducing side effects and improving outcomes. They are not completely without side effects, however, with the increased activity of the immune system causing an increased incidence of autoimmune conditions. One group of treatments, the immune checkpoint inhibitors, block certain cell surface proteins that can be present on T-cells or are overexpressed in cancer cells to prevent apoptosis. Blocking these receptors systemically, however, results in immunologic enhancement. Here we present a case of new-onset myasthenia gravis associated with pembrolizumab therapy, representing a reminder of both the wide range of possibilities and the potential severity of these immune-related adverse events.

A 75-year-old female with a history of metastatic renal clear cell carcinoma s/p resection and now on pembrolizumab presented to the emergency department complaining of dysphagia, shortness of breath with orthopnea and both blurry vision and double vision, with symptoms going on for 5-7 days. On exam, she was in no acute respiratory distress but with notable drooping of the right eyelid. Echocardiogram showed a normal ejection fraction without wall motion abnormalities. Blood work was largely normal other than a creatine kinase level > 1000. She was admitted to the hospital with concerns of new onset myasthenia gravis. Negative inspiratory flow (NIF) was -15 the following morning, and she was ultimately transferred to the ICU. A few days into her hospital stay her anti-AchR antibody titer was noted to be elevated.

Patient required non-invasive positive pressure ventilation and transfer to the ICU due to her respiratory status. She was given five-day courses of steroids and IVIG, and then subsequently started on pyridostigmine, with improvement in her NIF to -60 and her forced vital capacity (FCV) to 950 mL. She was ultimately transferred out of the ICU to the oncology service with NIPPV only required at night, but later in her hospital stay her respiratory status decompensated again, and she chose comfort care rather than an escalation in respiratory support. She passed away in the hospital.

This case presents an example of the wide range of potential immune-related adverse events from immune checkpoint therapies such as pembrolizumab, of which clinicians must always be cognizant when evaluating a patient on one of these therapies. It also highlights the high index of suspicion clinicians must have for myasthenic crisis in patients presenting with the classic symptoms, with these patients often rapidly needing disease modifying therapies such as steroids, IVIG, or plasmapheresis.

Comments

2025 Research Day Corewell Health West, Grand Rapids, MI, May 9, 2025. Abstract 1846

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