Abstract Details

Title Immune Checkpoint Inhibitor Induced Myasthenia Gravis-like Clinical Presentation: A Single Center Case Series

Topic Neuromuscular and Clinical Neurophysiology (EMG)

Presentation(s) P2 - Poster Session 2 (11:45 AM-12:45 PM)

Poster/Presentation
Number 9-001

Objective To characterize immune checkpoint inhibitor (ICI) induced myasthenia gravis (MG)-like clinical presentation and overlap manifestations with myositis and/or myocarditis.

Background ICI induced MG-like symptoms are associated with high fatality rate (up to 40-60%) when overlapping with myositis and myocarditis. Understanding this condition is critical to developing treatment strategies.

Design/Methods We examined 21 patients who presented to our medical center with ICI induced MG-like symptoms from April 2023 to July 2025. Clinical, laboratory, and electrodiagnostic findings were evaluated. Treatment regimens and outcomes were analyzed.

Results 86% of cases overlapped with myositis, 76% overlapped with myositis and myocarditis. 71% survived 90 days. Most common symptoms were proximal weakness (71%), myalgia (67%), dyspnea (52%), ptosis (38%), and respiratory failure (33%). Time from ICI treatment to symptom onset was shorter when overlapped with myocarditis (days, 22 vs 105, p=0.007). Peak CK and Troponin levels were higher with myocarditis (CK, 412 vs 1694, P= 0.008; Troponin, 32 vs 1859, p= 0.0001). Acetylcholine receptor (AChR) antibodies were frequently detected (46%). Abnormal decrement on repetitive nerve stimulation (RNS) was found in 3 patients (2 overlapped with myocarditis and myositis, 1 overlapped with myositis). Most patients were off chronic immunosuppression by 12 weeks after index admission. No recurrent symptoms of MG or myositis in surviving patients. No observed difference in chronic clinical course in patients with or without positive AChR antibody on diagnosis, or in patients with or without abnormal RNS. All patients treated with abatacept and ruxolitinib for myocarditis survived (n=6).

Conclusions ICI induced MG-like symptoms often present with concurrent myotoxicity. Most patients demonstrated a monophasic clinical course despite AChR antibody status or evidence of abnormal RNS on symptom onset. These differences from idiopathic MG should be confirmed in prospective cohorts to guide acute treatment strategies and prevent unnecessary long-term immunosuppression which could obliterate the anti-tumor effect of ICI.

Authors/Disclosures
Gabriela Figueiredo Pucci, MD PRESENTER	Dr. Figueiredo Pucci has nothing to disclose.
Joshua Levenson, MD	Dr. Levenson has nothing to disclose.
Brendan L. McNeish, MD	Dr. McNeish has received research support from NIH.
David Lacomis, MD, FAAN (UPMC Neurology)	Dr. Lacomis has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Cytokinetics. The institution of Dr. Lacomis has received research support from Mitsubishi Tanabe. The institution of Dr. Lacomis has received research support from NIH. Dr. Lacomis has received publishing royalties from a publication relating to health care.
Fang Sun, PhD, BM (UPMC Neurology)	Dr. Sun has nothing to disclose.

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