Seropositive Neuromyelitis Optica in a Case of Undiagnosed Ankylosing Spondylitis: A Neuro-Rheumatological Conundrum

Abstract

Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune astrocytopathy against foot processes of aquaporin-4 (AQP4) water channels. Patients with NMOSD tend to have other coexisting autoimmune/connective tissue diseases. However, AQP-4-antibody-positive NMOSD coexisting with ankylosing spondylitis (AS) is rare. AS is an immunemediated disorder, a subset of axial spondyloarthropathies, which commonly manifests as chronic inflammatory back pain in young people, and it has a strong association with HLA-B27. In this study, a 35-year-old Indian man with an undiagnosed progressive axial spondyloarthropathy (i.e., AS) is reported presenting with acute-onset longitudinally extensive transverse myelitis, a clinical subset of NMOSD.