Myocarditis and Myasthenia Gravis Induced by Camrelizumab in a Patient With Metastatic B2 Thymoma: A Case Report

Thymoma is a rare malignant tumor originating from the thymus epithelium. In recent years, immune checkpoint inhibitors have become an indispensable treatment for cancer. However, the efficacy and adverse events of immunotherapy for thymoma have not been widely evaluated. A 53-year-old Chinese man who was diagnosed with metastatic B2 thymomas since March 2023. He received chemotherapy plus anlotinib for four cycles since May 5, 2023, and underwent radiotherapy from May 23, 2023 to June 30, 2023. However, the treatment was not satisfactory. Thus, we detected PD-L1 expression in tumors; immunohistochemical examination on the tumor revealed a high PD-L1 expression in 60% of tumor cells. He presented symptoms of palpitation, gasping, fatigue, diplopia, and eyelid ptosis. Additionally, he was found to have significantly elevated levels of serum cardiac troponin, creatine kinase, creatine kinase isoenzymes, N-terminal pro brain natriuretic peptide, and anti-acetylcholine receptor antibody. He was eventually diagnosed with immune-related myocarditis and myasthenia gravis. Finally, the patient was discharged after treatment with glucocorticoids, immunoglobulin, and pyridostigmine. Although immune checkpoint inhibitors have achieved similar anti-tumor effects in thymomas as in other solid tumors, they may be closely associated with serious immune-related adverse events, so special caution is required when using immune checkpoint inhibitors in thymoma patients.