Circulating IgM rheumatoid factors in patients with primary Sjögren's syndrome

The importance of circulating rheumatoid factors (RF) in primary Sjögren's syndrome (primary SS) was evaluated retrospectively by examining medical case records of 80 consecutive patients. Increased levels of IgM RF, determined by the Waaler test, the latex fixation test and/or the ELISA test, were found in 47 patients (59%). Follow-up examination of the 41 patients in whom more than one (mean 4.9 (2-12)) RF determination over at least a two-year period (mean 5.6 (2-13) was present, showed that 12/41 patients (29%) were permanently RF-negative, 7/41 (17%) exhibited both positive and negative RF values and 22/41 (54%) were permanently RF positive. Variations in IgM RF levels were unrelated to disease duration. Except for involvement of joints, extraglandular manifestations were more common in patients with increased levels of RF. This finding, however, was only significant within the group of more rarely occurring extraglandular manifestations (serositis, interstitial nephritis, cutaneous vasculitis, lymphoproliferative disorders and intermittent fever) (p less than 0.01). IgM RF levels were likewise positively correlated (p less than 0.001) to positivity of IgG antinuclear antibodies as well as to the plasma concentrations of immunoglobulins.