Fatal Outcome of Pembrolizumab-Related Cytokine Release Syndrome in a Patient With Concurrent Parainfluenza Infection

Pembrolizumab improves response and survival in triple-negative breast cancer; however, severe immune-related adverse effects (irAEs) are concerning. We present a case of a patient with triple-negative breast cancer on neoadjuvant pembrolizumab who developed high fever and chills after the seventh cycle. Rapid deterioration occurred, leading to multiple-organ failure. Parainfluenza virus was identified in various cultures, and interleukin-6 levels were disproportionately elevated (79 014 ng/L), resulting in the diagnosis of cytokine release syndrome. This case underscores the need for vigilant monitoring and care when parainfluenza infection coincides with immune checkpoint inhibitors due to potentiated immune responses and fatal complications.