Immune Checkpoint Inhibitor-Induced Concomitant Polyradiculoneuritis and Myocarditis With Positive Anti-Titin Antibodies: A Case Report and Literature Review.

BACKGROUND: Immune-related adverse events (irAEs) induced by immune checkpoint inhibitors vary widely, raising diagnostic challenges. The management of suspected irAEs requires close collaboration between oncologists and organ specialists. Rarely, irAEs can occur as overlap syndromes and may require intensive care. CASE SUMMARY: A 69-year-old man required intensive care for severe overlap syndrome induced by a programmed death-ligand 1 inhibitor. The presentation as recurrent hypercapnic coma complicated the diagnosis of polyradiculoneuritis combined with myocarditis. The finding of anti-titin autoantibodies assisted in the diagnosis. The patient was successfully treated with corticosteroids, polyvalent immunoglobulins, abatacept, and ruxolitinib. The irAEs abated but the polypharmacy contributed to the development of fatal hemorrhagic shock. CONCLUSIONS: This is the first reported case of seropositive, overlap irAEs consisting of myocarditis and polyradiculoneuritis. Early immunosuppressive therapy can alleviate irAEs but can also lead to serious complications in frail patients. This underscores the importance of carefully balancing expected therapeutic benefits against potential risks.