RT Journal Article
SR Electronic
T1 Inflammatory myopathy with myasthenia gravis
JF Neurology - Neuroimmunology Neuroinflammation
JO Neurol Neuroimmunol Neuroinflamm
FD Lippincott Williams & Wilkins
SP e535
DO 10.1212/NXI.0000000000000535
VO 6
IS 2
A1 Naohiro Uchio
A1 Kenichiro Taira
A1 Chiseko Ikenaga
A1 Masato Kadoya
A1 Atsushi Unuma
A1 Kenji Yoshida
A1 Setsu Nakatani-Enomoto
A1 Yuki Hatanaka
A1 Yasuhisa Sakurai
A1 Yasushi Shiio
A1 Kenichi Kaida
A1 Akatsuki Kubota
A1 Tatsushi Toda
A1 Jun Shimizu
YR 2019
UL http://nn.neurology.org/content/6/2/e535.abstract
AB Objective To provide evidence that idiopathic inflammatory myopathy (IM) with myasthenia gravis (MG) frequently shows thymoma association and polymyositis (PM) pathology and shares clinicopathologic characteristics with IM induced by immune checkpoint inhibitors (ICIs).Methods We analyzed the clinicopathologic features of 10 patients with idiopathic IM and MG identified in 970 consecutive patients with biopsy-proven IM.Results Seven patients (70%) had thymoma. IM and MG were diagnosed with more than 5-year time difference in 6 thymomatous patients and within 1 year in 1 thymomatous and 3 nonthymomatous patients. Seven thymomatous patients showed rhabdomyolysis-like features with respiratory failure (4/7), dropped head (3/7), cardiac involvement (2/7), and positive anti–acetylcholine receptor (anti-AChR) and anti-titin antibodies (7/7 and 4/6, respectively) but rarely showed ocular symptoms (2/7) or decremental repetitive nerve stimulation (RNS) responses (1/7) at IM diagnosis. Three nonthymomatous patients showed acute cardiorespiratory failure with rhabdomyolysis-like features (1/3), positive anti-AChR and anti-titin antibodies (3/2 and 2/2, respectively), and fluctuating weakness of the skeletal muscle without ocular symptoms (3/3). Muscle pathology showed a PM pathology with infiltration of CD8-positive CD45RA-negative T-lymphocytes (9/9), scattered endomysial programmed cell death 1 (PD-1)–positive cells (9/9), and overexpression of programmed cell death ligand 1 (PD-L1) on the sarcolemma of muscle fibers around the infiltrating PD-1–positive cells (7/9).Conclusion Rhabdomyolysis-like features, positive anti-AChR antibody without decremental RNS responses, and PD-L1 overexpression are possible characteristics shared by ICI-induced IM. Frequent thymoma association in patients with idiopathic IM and MG may suggest thymoma-related immunopathogenic mechanisms, including dysregulation of the immune checkpoint pathway.anti-AChR=anti–acetylcholine receptor; CK=creatine kinase; CTLA-4=cytotoxic T-lymphocyte–associated protein 4; IBM=inclusion body myositis; ICI=immune checkpoint inhibitor; IM=inflammatory myopathy; MG=myasthenia gravis; MHC=major histocompatibility complex; MSA=myositis-specific autoantibody; PD-1=programmed cell death 1; PD-L1=programmed cell death ligand 1; PM=polymyositis; PSL=prednisolone; RNS=repetitive nerve stimulation; SFEMG=single-fiber electromyogram