Immune Checkpoint Inhibitor Associated Myopathy with Concurrent Myocardial Injury: A Retrospective Cohort Study

To characterize immune checkpoint inhibitor (ICI) myopathy complicated by myocardial injury.

Retrospective analysis of 16 patients who were diagnosed with ICI myopathy complicated by myocardial injury at Beijing Tsinghua Changgung Hospital from 2020 to 2025.

The cohort comprised 16 patients (male:female ratio: 10:6; mean age 68 years) who developed at a median of 37 days after the initial immunotherapy. The initial clinical manifestations included ptosis in 43.8% (n=7) of the patients, bulbar muscle involvement in 12.5% (n=2), and respiratory muscle impairment in 18.8% (n=3). All patients demonstrated cardiac involvement. Laboratory findings revealed elevated creatine kinase (CK) levels (mean 2190.9 U/L), CK-MB isoenzyme (mean 79.1 ng/mL) and high-sensitivity troponin T levels (hs-TnT) (mean 1.077 ng/mL) in all patients. Anti-acetylcholine receptor antibody positivity was observed in 25% (1/4) and anti-titin antibody positivity in 50% (2/4) of the tested patients. Myopathic changes were identified in 50% of patients (3/6), and one patient exhibited a decremental response to low-frequency repetitive nerve stimulation with an incremental response to high-frequency stimulation. During the course of hormone therapy, we observed a previously unreported discordant phenomenon in 50% of patients (n=8), characterized by a rebound elevation in the CK-MB isoenzyme occurring concurrently with a gradual decline in total CK levels.

ICI myopathy is a distinct immune-mediated disorder that emerges following cancer immunotherapy. It is characterized by skeletal and cardiac muscle involvement, with a hallmark clinical feature of nonfluctuating ptosis. It is particularly noteworthy that even patients presenting with mild clinical symptoms and only minor elevations in CK or cardiac enzymes should be carefully evaluated for electrocardiographic abnormalities and monitored for malignant arrhythmias. Early diagnosis, prompt intervention, and rigorous monitoring of laboratory parameters and cardiac rhythms during the acute phase are essential for improving outcomes.