Aquaporin-4 antibody positive neuromyelitis optica spectrum disorder associated with esophageal cancer

Autoimmune diseases are sometimes associated with neoplasms. A 70-year-old Japanese woman with myelitis, seropositive for aquaporin-4 (AQP4) antibody, was diagnosed with neuromyelitis optica spectrum disorder (NMOSD); thereafter an esophageal squamous cell carcinoma was identified. Immunohistochemically, her cancer was anti-AQP4 antibody negative. Her symptoms, imaging findings and AQP4 titer markedly improved with corticosteroid and anti-cancer therapies. Although AQP4 may be a paraneoplastic antigen, paraneoplastic syndrome could not be definitively diagnosed in this case. Nevertheless, this is the first report of an association between AQP4 antibody-seropositive NMOSD and esophageal cancer. The possibility of underlying malignancy should be considered in patients diagnosed with NMOSD.