Steroid-responsive Nivolumab-induced Involuntary Movement with Anti-thyroid Antibodies

We herein report a 68-year-old man with neurologic immune-related adverse events (irAEs) who exhibited nivolumab-induced steroid-responsive progressive ataxia, tremor, and anti-thyroid antibodies. His symptoms matched abnormalities on N-isopropyl-p-(123I)-iodoamphetamine single-photon emission computed tomography (SPECT) and dopamine transporter SPECT. Based on these clinical findings, we diagnosed the patient with a condition similar to the cerebellar type of Hashimoto's encephalopathy with nivolumab-induced anti-thyroid antibodies. Neurologic irAEs can be difficult to diagnose due to their varied clinical courses and lack of specific examinations. Therefore, a comprehensive approach, including assessments of autoantibodies and functional imaging, might be important for the diagnosis of neurologic irAEs.