Objective:

To report a case of successful rescue treatment with eculizumab for a patient with tislelizumab-related MMM overlap syndrome and to review existing literature on the use of complement inhibitor therapy for ICI-related myasthenia gravis, highlighting the significance of this case in advancing treatment options.

Key Findings:

• The patient showed rapid clinical improvement after receiving eculizumab, achieving minimal symptom expression, indicating the potential of eculizumab in similar cases.
• This case represents the first reported use of eculizumab for tislelizumab-related MMM overlap syndrome, suggesting a new avenue for treatment.

Interpretation:

Eculizumab may be a promising rescue option for patients with ICI-MMM, warranting further prospective evaluation.

Limitations:

• The case lacks histopathological confirmation for myocarditis and myositis, which may affect diagnostic accuracy.
• Findings are based on a single patient case and may not be generalizable, underscoring the need for larger studies.

Conclusion:

Eculizumab demonstrated rapid efficacy in a patient with severe ICI-MMM, suggesting its potential as a rescue therapy and highlighting the need for further prospective evaluation to confirm these findings.