Rheumatoid Arthritis: A Rare Cause of Pachymeningitis and Optic Neuritis.

Introduction: Rheumatoid pachymeningitis and optic neuritis are rare complications of rheumatoid arthritis (RA) and are a diagnosis of exclusion. Case description: A 75-year-old male with a history of seronegative RA presented to the emergency department with left eye pain and blurry vision lasting two days. He had been diagnosed with seronegative RA around nine months previously. His blood pressure was elevated at 204/75 mmHg upon arrival. Physical examination revealed left conjunctival injection, mild ptosis, painful extraocular movements and tenderness over the orbit and sinuses. Initial treatments included painkillers and intravenous labetalol, which alleviated his symptoms and decreased his blood pressure. Laboratory tests showed a C-reactive protein of 2.5 mg/dl and an erythrocyte sedimentation rate of 32 mm/h, with other blood work unremarkable. A computed tomography (CT) angiogram of the head and neck showed no high-grade stenosis. Given his RA history, initial concerns included scleritis. A magnetic resonance imaging (MRI) of the brain and orbit revealed inflammation around the left optic nerve, and pachymeningitis at the left cerebral convexity and interhemispheric fissure, suggesting hypertrophic pachymeningitis. An ophthalmologic examination was unremarkable. Treatment was adjusted to include pulse doses of intravenous methylprednisolone for optic neuritis, resulting in significant pain relief. Though inadequate for complete testing, a lumbar puncture indicated an inflammatory disorder with elevated glucose (199 mg/dl), protein (109 mg/dl), and unremarkable WBC/RBC and Gram staining. Cytology and culture were unremarkable. The most likely diagnosis at this point was rheumatological meningitis and rheumatological optic neuritis. The patient improved markedly with high-dose steroids over four days and was discharged on prednisone. Conclusion: In cases of optic neuritis and pachymeningitis, RA should remain on the differential in patients with or without a prior diagnosis. LEARNING POINTS: Rheumatoid arthritis (RA) is a systemic disease but can rarely cause neurological involvement.Pachymeningitis is an inflammation of the dura mater, rarely caused by RA.Optic neuritis can also rarely be caused by RA and responds to steroids.