Autoantibodies in the sicca syndrome (primary Sjögren's syndrome).

IgA and IgM rheumatoid factors as well as antibodies to Ro and La were measured in 37 patients with the sicca syndrome and 9 patients with Sjögren's syndrome secondary to rheumatoid arthritis. Positive results were found in 84% (IgA rheumatoid factor), 76% (IgM rheumatoid factor), 62% (Ro), and 50% (La) of patients with the sicca syndrome. There was no significant difference in the frequency of positive results in patients with glandular versus extraglandular disease. Antibodies to La invariably occurred in patients with antibodies to Ro. In addition, patients who were anti-Ro positive also had significantly higher IgA (p less than 0.05) and IgM (p less than 0.01) rheumatoid factor activity. Since 81% of the sicca patients were concordant for 3 of the 4 antibodies tested, production of these autoantibodies appears to be related.