A case of immune-related adverse events, thyroid dysfunction, myocarditis with myositis, and myasthenia gravis overlap syndrome following serplulimab administration for lung adenocarcinoma

BACKGROUND: Serplulimab is an immune checkpoint inhibitor (ICI) that blocks inhibitors, augmenting anti-tumor immunity but also carrying risks of immune-related adverse events (irAEs). While neuromuscular and cardiac toxicities are rare, their co-occurrence can lead to high mortality. In this article, we report a patient with multiorgan irAEs after treatment with chemoimmunotherapy. CASE PRESENTATION: A 49-year-old man with lung adenocarcinoma developed thyroid dysfunction 3 weeks after initial chemoimmunotherapy (carboplatin, pemetrexed, serplulimab). Following the second cycle, he presented with speech difficulty, bilateral ptosis, dysphagia, fatigue, and elevated creatine kinase (2112 U/L) and troponin T (570 ng/L), suggesting ICI-induced thyroid dysfunction, myocarditis, myositis, and myasthenia gravis overlap syndrome. Brain magnetic resonance imaging was negative. He received methylprednisolone with initial improvement, but troponin elevation recurred after premature steroid discontinuation. Successful treatment was achieved with high-dose methylprednisolone and intravenous immunoglobulin, leading to normalized cardiac markers. CONCLUSIONS: The serplulimab-induced multiorgan irAEs necessitates enhanced monitoring, biomarker research, and multidisciplinary collaboration to optimize safety and antitumor efficacy.