Neuromyelitis optica spectrum disorder with positive anti-aquaporin-4 antibodies in the context of long-standing rheumatoid arthritis: A case report.

Neuromyelitis optica spectrum disorder (NMOSD) associated with rheumatoid arthritis (RA) is an uncommon inflammatory demyelinating condition that presents a diagnostic challenge. We report the case of a woman with a 10-year history of RA and a six-year progressive paraparesis. Magnetic resonance imaging revealed longitudinally extensive transverse myelitis from T4 to the filum terminale. Cerebrospinal fluid analysis showed negative oligoclonal bands and hyperproteinorachia without pleocytosis. The immunological profile confirmed positivity for anti-aquaporin-4 antibodies (62 UI/mL), along with markedly elevated rheumatoid factor and anti-CCP. Following intravenous methylprednisolone, a partial motor recovery to 3/5 was achieved. The patient voluntarily discontinued medical follow-up, preventing the initiation of maintenance immunosuppressive therapy. The onset of atypical neurological symptoms in patients with systemic autoimmunity requires a high clinical suspicion of NMOSD, regardless of the stability of the underlying arthropathy. Early diagnosis and strict treatment adherence are critical to prevent cumulative structural damage and permanent disability.