Immune-related myositis induced by immune checkpoint inhibitors: two case reports and literature review / 中华风湿病学杂志

ABSTRACT

Objective:To investigate the clinical features and treatment status of immune-related myositis (IRM) caused by immune checkpoint inhibitors (ICIs) in order to improve the diagnosis and treatment rate of the disease.Methods:Two cases of IRM combined with the diagnosis and treatment were described and the literature about IRM in the past 10 years was reviewed, and the clinical data of 59 patients were analyzed.Results:IRM was more common in males, with a total of 47 (79.7%). IRM usually occurred after 45 days of medication or after two doses. The clinical manifestations were mainly myalgia and muscle weakness, which were more common in the limbs. The initial symptoms were ptosis and diplopia. Fifty patients (84.7%) had serum creatine kinase (CK) levels higher than twice the upper limit of normal (UNL). In immunological examinations, 18 patients were found to be positive for anti-rhabdoid muscle antibody (AsM-Ab), while most of the myositisspecific antibodies (MSAs) and myositis-associated antibodies (MAAs) were negative. Thirty-four patients (75.6%) had abnormal EMG, and most patients showed myogenic injury. Muscle magnetic resonance imaging (MRI) showed muscle edema and inflammation in 8 patients. Muscle biopsies from 18 (45.0%) patients showed varying degrees of necrotic myofibers. Fifty-seven patients (96.6%) discontinued ICIs after developing IRM, 54(91.5%) received cortico-steroids, and 20(33.9%) received other treatments including intravenous immuno-globulin (IVIG), plasma exchange.Conclusion:IRM can occur in the early stage of ICIs treatment. Electro-myography, muscle MRI and muscle biopsy in suspicious cases can improve the diagnosis rate of the disease. Early use of corticoteroid, IVIG and other immunotherapy can effectively alleviate the disease.