Circulating IgA- and IgM-rheumatoid factors in patients with primary Sjögren syndrome. Correlation to extraglandular manifestations.

IgM- and IgA-rheumatoid factors (RF) were determined by ELISA technique in 40 consecutive patients with primary Sjögren syndrome (primary SS), all fulfilling the Copenhagen diagnostic criteria. Increased concentrations of IgM-RF were found in 25 patients (63%) (median concentration: 85 IU/ml, range 11-302 IU/ml). Increased concentrations of IgA-RF were found in 22 of the patients (55%) (median concentration: 100 AU/ml, range 25-255 AU/ml). The levels of IgM- and IgA-RF were closely correlated (r = 0.82, p less than 0.001). IgM-RF (p = 0.037), but not IgA-RF (p = 0.17), was significantly correlated to the presence of antinuclear antibodies (ANA). In contrast, IgA-RF (p = 0.002), but not IgM RF (p = 0.068), was significantly correlated to the presence of hypergammaglobulinemia. The most common extraglandular manifestations were: arthralgia/synovitis (60%), myalgia/myositis (28%), Raynaud's phenomenon (20%) and pulmonary manifestations (15%). Concentrations of both IgM-RF (r = 0.43, p less than 0.01) and IgA-RF (r = 0.57, p less than 0.001) were correlated to the number of extraglandular manifestations present in each patient.