Myocarditis and myasthenia gravis induced by immune checkpoint inhibitor in a patient with relapsed thymoma: A case report

Immune checkpoint inhibitors (ICIs)‐targeting CTLA4 and PD1 constitute a promising class of cancer treatment but are associated with several immune‐related adverse events (irAEs). A 55‐year‐old male patient with relapse thymoma was subjected to ICI therapy (PD‐1 antibody), 2 weeks later, the patient started to manifest including droopy eyelids, weak neck, arms, and legs, and shortness of breath. Then the patient was admitted to the hospital because of the MG symptoms. Arterial blood gases (ABGs) revealed the presence of hypercapnia. Noninvasive ventilation was utilized for respiratory support. At admission, increased serum troponin levels, coupled with interventricular conduction abnormalities were observed. On the second day after admission, the patient developed transient loss of consciousness and twitching of the muscles, and electrocardiography monitoring showed intermittent third‐degree atrioventricular block and ventricular pause necessitating temporary cardiac pacing. After excluding the possibility of acute coronary syndrome, intravenous steroids, intravenous immunoglobulin, pyridostigmine, and mycophenolate mofetil were sequentially initiated. 2 weeks later after treatment initiation, cardiac biomarkers and conduction abnormalities were recovered. 7 weeks later, MG symptoms were markedly improved. ICI‐related MG and myocarditis can be life‐threatening without appropriate management and clinicians should have a high index of suspicion for these irAEs in cancer patients receiving ICIs therapy. Steroids remain the cornerstone in the current management of irAEs due to the fast onset of action and high efficacy. However, in severe and refractory cases where no improvement is achieved despite high‐dose steroids, alternative immunosuppressants should be considered.