Neuromyelitis optica spectrum disorder in a patient with ankylosing spondylitis: A case report.

Neuromyelitis optica spectrum disorder is an autoimmune disease which tends to have other coexisting autoimmune or connective tissue diseases. However, coexisting with ankylosing spondylitis is rare. Here, we report a 57-year-old man with concomitant autoantibodies against aquaporin 4-positive neuromyelitis optica spectrum disorder and HLA-B27-positive ankylosing spondylitis.