Systemic AA Amyloidosis Following Immune Checkpoint Inhibitor Therapy for Lung Carcinosarcoma: An Autopsy Case and Review of the Literature.

AA amyloidosis is a rare but serious complication of chronic inflammation. We report an autopsy case of a 68-year-old man without a documented history of inflammatory disease who developed lung carcinosarcoma and achieved a durable complete response after sequential immune checkpoint inhibitor (ICI) therapy. Despite tumor control, the patient developed a chronic intestinal pseudo-obstruction, persistent C-reactive protein elevation, progressive renal dysfunction, and later aspiration pneumonia. Autopsy revealed systemic AA amyloid deposition, predominantly in the intestines and kidneys, chronic thyroiditis, and tubulointerstitial nephritis. This case raises the possibility that prolonged inflammation during and after ICI therapy contributes to systemic AA amyloidosis.