Selective polyclonal increase of immunoglobulin G1 subclass: a link with Sjögren's syndrome.

A selective polyclonal increase in IgG1 has been described previously in a group of patients with connective tissue disease; nine of the 16 patients had a prior diagnosis of systemic lupus erythematosus (SLE). A detailed clinical and serological study of 32 patients with this immunoglobulin abnormality has now been made. Most cases showed a characteristic autoantibody profile of antinuclear antibody, rheumatoid factor, and antibodies to Ro and La. Sjögren's syndrome was diagnosed as 'definite' in 16 cases and 'possible' in seven cases by Fox's criteria. The remainder had unclassified connective tissue disease (three), rheumatoid arthritis with dry eyes (two), SLE (one), scleroderma (two), and Raynaud's disease (one). Extraglandular features were invariably present in patients with primary Sjögren's syndrome. The highest concentrations of IgG1 were found in patients with the shortest disease duration. Selective polyclonal increase of IgG1 should alert the doctor to the development of Sjögren's syndrome, usually with extraglandular disease and antibodies to Ro and La.