AQP4 and Autoimmunity: Second, thyroperoxidase antibodies and other autoantibodies are detectable in up to half of AQP4-IgG-seropositive NMOSD patients, with approximately one-third exhibiting comorbid autoimmune disorders such as thyroiditis, systemic lupus erythematosus, or Sjögren’s syndrome (Wingerchuk and Lucchinetti, 2022).