Primary Sjögren's Syndrome Revealed During the Evaluation of Paroxysmal Tonic Spasms Leading to the Diagnosis of Seronegative Neuromyelitis Optica Spectrum Disorder: A Case Report.

Neuromyelitis optica spectrum disorder (NMOSD) may coexist with other autoimmune diseases, including primary Sjögren's syndrome. We report a 52-year-old female presenting with sicca symptoms leading to the diagnosis of primary Sjögren's syndrome based on a positive Schirmer's test, grade III sialadenitis, and anti-SSB antibodies. Further evaluation revealed a history of optic neuritis and paroxysmal tonic spasms involving the limbs, associated with intractable hiccups and acute myelopathy. Magnetic resonance imaging showed brain and spinal lesions suggestive of NMOSD, with negative aquaporin-4 (AQP4) and anti-myelin oligodendrocyte glycoprotein (MOG) antibodies. A diagnosis of seronegative NMOSD associated with primary Sjögren's syndrome was retained. Immunosuppressive therapy led to clinical improvement. This case highlights that paroxysmal tonic spasms may reveal NMOSD in patients with Sjögren's syndrome.