Abstract Details

Title A Case of Pembrolizumab-Induced Autoimmune Necrotizing Myopathy

Topic Neuromuscular and Clinical Neurophysiology (EMG)

Presentation(s) P3 - Poster Session 3 (5:30 PM-6:30 PM)

Poster/Presentation
Number 12-004

Objective

To describe a case of pembrolizumab-induced autoimmune necrotizing myopathy.

Background Immune Checkpoint Inhibitors (ICI), especially Programmed Death-1 (PD-1) inhibitors, are increasingly used for cancer immunotherapy treatment and been associated with various central or peripheral nervous system autoimmune disorders, in particular the neuromuscular system. This mechanism remains unclear due to insufficient studies related to this process. We present a case of pembrolizumab-induced autoimmune necrotizing myositis, to contribute to the growing literature.

Design/Methods Case report.

Results A 77 year-old man with a history of stage-IV melanoma presented progressive weakness, two weeks after receiving his first dose of pembrolizumab. He developed new onset of progressively worsening bilateral ptosis, dysarthria, ophthalmoplegia, facial diplegia, proximal > distal limb weakness, and respiratory insufficiency. Laboratory work-up revealed AST 492 U/L, ALT 256 U/L, and CPK 8284 U/L. His second dose of pembrolizumab was held. He was intubated and placed on mechanical ventilation, and was started on combined therapy with IVIg and IV methylprednisolone for five days, followed by four plasmapheresis treatments. He had negative acetylcholine receptor antibodies. Right vastus lateralis muscle biopsy revealed moderately severe necrotizing myopathy and mild type II fiber atrophy. CT of chest negative for thymoma; MRI of brain negative for ischemia. The patient started experiencing clinical and laboratory improvement (AST 36 U/L, ALT 130, CK 250 U/L), within 4 days of combined IVIg and steroid treatment. His hospital course was complicated by acute respiratory failure, altered mental status resulting in tracheostomy and percutaneous endoscopic gastrostomy, and septic shock.

Conclusions Autoimmune myopathy appears to be the commonest neuromuscular disorder associated with ICI treatment. It is important to further characterize these myopathies, in terms of myopathology and serology. Rapid diagnosis is essential to initiate prompt therapy as well as discontinuation of the immune checkpoint inhibitor.

Authors/Disclosures
Nita Chen, MD (Newport Neurology Associates) PRESENTER	Dr. Chen has nothing to disclose.
Sarita Said-Said, MD, FAAN (Palouse Neurology)	Dr. Said-Said has received personal compensation in the range of $0-$499 for serving as an officer or member of the Board of Directors for Gritman Medical Center.
	No disclosure on file
Tahseen Mozaffar, MD, FAAN (University of California Irvine)	Dr. Mozaffar has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Alexion Pharmaceuticals. Dr. Mozaffar has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Argenx. Dr. Mozaffar has received personal compensation in the range of $10,000-$49,999 for serving as a Consultant for Sanofi-Genzyme. Dr. Mozaffar has received personal compensation in the range of $10,000-$49,999 for serving as a Consultant for Amicus. Dr. Mozaffar has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Grifols. Dr. Mozaffar has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Astellas Gene Therapy. Dr. Mozaffar has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Bayer. Dr. Mozaffar has received personal compensation in the range of $10,000-$49,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Sarepta. Dr. Mozaffar has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Applied Therapeutics. The institution of Dr. Mozaffar has received research support from NIH. The institution of Dr. Mozaffar has received research support from Muscular Dystrophy Association. The institution of Dr. Mozaffar has received research support from Sanofi. The institution of Dr. Mozaffar has received research support from Argenx. The institution of Dr. Mozaffar has received research support from Amicus Therapeutics. The institution of Dr. Mozaffar has received research support from Astellas Gene Therpay. The institution of Dr. Mozaffar has received research support from Cartesian. The institution of Dr. Mozaffar has received research support from Cabaletta. Dr. Mozaffar has received personal compensation in the range of $500-$4,999 for serving as a Study Section Member with NIH.

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