Presence of Antinuclear Antibodies in the Cerebrospinal Fluid and in the Serum in a Patient With Sjögren's Syndrome and Systemic Lupus: A Case Report.

Systemic lupus erythematosus (SLE) may overlap with Sjögren's syndrome (SS), leading to complex systemic involvement, including neurological and pulmonary manifestations. We report a 60-year-old woman with a 10-year history of SLE-SS overlap presenting with headaches and bilateral visual impairment. Hydroxychloroquine (HCQ) had been discontinued 4 months prior due to HCQ-related optic neuropathy confirmed on optical coherence tomography (OCT). Ophthalmologic evaluation revealed bilateral optic neuritis. Immunological testing showed high-titre antinuclear antibodies (ANAs) in both serum (1:640) and cerebrospinal fluid (CSF) (1:320), with positive anti-dsDNA, anti-SSA/Ro52, anti-Sm/RNP, and anti-ribosomal P antibodies. CSF analysis was normal, without pleocytosis, hyperproteinorrhachia, oligoclonal bands, or intrathecal IgG synthesis (IgG index 0.61). Brain MRI showed non-enhancing periventricular demyelinating lesions, and thoracic CT revealed bilateral bronchiectasis. The patient received intravenous methylprednisolone (500 mg/day × 3 days) followed by oral corticosteroids, with leflunomide added as an immunomodulatory agent given the overlap syndrome context, resulting in a favourable clinical outcome. The absence of intrathecal immunoglobulin synthesis and oligoclonal bands supports blood-brain barrier dysfunction rather than a primary demyelinating process, highlighting the diagnostic challenge in SLE-SS overlap. ANA detection in CSF may serve as a supportive marker for neuropsychiatric lupus (NPSLE) in overlap syndromes.