Abstract
The histological features of the synovial membrane in rheumatoid arthritis (RA) are shared by other chronic inflammatory joint diseases, so that diagnostic differentiation is impossible. Examination of the immunoglobulin class in the plasma cells present in inflamed synovial membranes, however, has shown differences. Synovial membranes from 12 patients were seropositive RA, eight with seronegative RA, eight with ankylosing spondylitis, five with psoriatic arthritis, and three with Reiter's syndrome have been compared by peroxidase-antiperoxidase (PAP) staining for immunoglobulin classes on routinely paraffin wax embedded sections. There were no significant differences in the percentages of plasma cells containing IgG of IgA between the diseases studied. There were, however, significantly more plasma cells containing IgM in patients with seropositive RA (2-34%) compared with those with seronegative RA (0-10%; p less than 0.002) and with other chronic synovitides (0-9%; p less than 0.002). The results show that it is possible to distinguish seropositive RA from other chronic inflammatory joint diseases by PAP staining for immunoglobulin classes in the plasma cells present in the inflamed synovial membrane.