Rheumatoid meningitis: a rare cause of unilateral pachymeningitis.

An 87-year-old woman with quiescent rheumatoid arthritis, not on immunosuppressive therapy, presented with unilateral arm weakness, confusion and visual hallucinations. There were no infective symptoms or history of malignancy. Cerebrospinal fluid (CSF) analysis demonstrated lymphocytosis and raised protein, without flow cytometric or cytological abnormalities. Viral, bacterial, mycobacterial and fungal testing of CSF and serum were negative. MRI brain indicated unilateral leptomeningeal enhancement. There was no evidence of occult malignancy on CT imaging of the chest, abdomen and pelvis. Rheumatoid factor and anticyclic citrullinated peptide were strongly positive. The patient declined meningeal biopsy but responded to treatment with corticosteroid therapy.