Immune checkpoint inhibitor-associated paraneoplastic cerebellar degeneration in a case of extensive-stage small-cell lung cancer with pre-existing anti-SOX1 antibody

Abstract

Neurological immune-related adverse events can manifest as paraneoplastic neurological syndrome (PNS), especially in patients with small-cell lung cancer (SCLC). We herein report a 73-year-old man with SCLC treated with an immune checkpoint inhibitor (ICI) combined with chemotherapy. Although the chemo-immunotherapy induced a favorable response to SCLC, he later developed acute cerebellar ataxia. He was diagnosed with paraneoplastic cerebellar degeneration associated with anti-Sry-like high mobility group box 1 (SOX1) autoantibody. The antibody was also identified in serum collected at the diagnosis of SCLC and before ICI administration, which retrospectively suggested that the patient was at risk of ICI-induced PNS. J. Med. Invest. 72 : 172-176, February, 2025