Comparable histological appearance of synovitis in seropositive and seronegative rheumatoid arthritis

To compare the histological characteristics of the synovium between seropositive and seronegative rheumatoid arthritis (RA), synovial tissue was obtained from 19 patients with rheumatoid factor-positive (RF+) RA, 11 with rheumatoid factor-negative (RF-)RA and 11 non-RA controls.

There were no differences in the frequency of each histological feature or histological scores between RF+ and RF-RA. However, significant differences in the frequency of histological findings such as lining cell proliferation and inflammatory cell infiltration were found both between RF+ RA and non-RA controls, and between RF-RA and non-RA controls. Analysis of clinical parameters and histology in all RA patients revealed that the level of serum C-reactive protein and the erythrocyte sedimentation rate were directly correlated with the inflammatory cellular infiltration score. Immunohistological staining using a monoclonal antibody against IgM rheumatoid factor (RF) was positive in some plasma cells in the synovium of both RF+ and RF-RA patients, while no IgM-RF-positive cells were observed in the synovium of non-RA controls.

RF serostatus does not necessarily reflect the histology of synovial inflammation.