Three-year follow-up of rheumatoid meningitis with matrix metalloprotease-9 levels in the serum and cerebrospinal fluid as indicators of disease activity: A case report.

Rheumatoid meningitis (RM) is an extra-articular complication of rheumatoid arthritis (RA). Although reports of RM sine arthritis exist, most patients with this presentation were diagnosed with RA within one year of RM onset. There are no established biomarkers reflecting the disease activity of RM. This case report highlights the elevation of matrix metalloprotease (MMP)-9 levels during the acute phase of RM and decline during remission. Additionally, this is the first case report of RA diagnosed three years after the onset of RM. It is important to further validate the utility of MMP-9 and conduct long-term follow-up of RM sine arthritis.