Anti-cyclic citrullinated peptide antibody in the cerebrospinal fluid in patients with rheumatoid arthritis who have central nervous system involvement.

Central nervous system (CNS) involvement, including encephalopathy, encephalitis, leptomeningitis, and pachymeningitis, in rheumatoid arthritis (RA) is rather rare. We report the case of a 61-year-old female with a history of RA in remission for 7 years, who presented with numbness, weakness of the left upper limb, dysarthria, and headache. Magnetic resonance imaging (MRI) of the brain showed meningeal enhancement in the frontal, parietal, and temporal lobes. Cerebrospinal fluid (CSF) examination detected high levels of both rheumatoid factor (RF) and anti-cyclic citrullinated peptide antibody (ACPA), with a high ACPA-immunoglobulin G index (> 2.0). She was diagnosed with rheumatoid meningitis. Following combined therapy with oral prednisolone and intravenous infusion of cyclophosphamide, her symptoms promptly improved. After treatment, RF and ACPA levels in the CSF were reduced, and MRI showed improvement of the meningeal structures. This case, along with existing literature, suggests that the ACPA level in the CSF may serve as a useful marker for diagnosing of CNS involvement in RA, as well as an index of effectiveness of the associated treatment.