Sjögren's syndrome in relation to other autoimmune diseases.

Autoimmune diseases can be divided into primary autoimmune diseases, in which the immune system is over-reactive, leading to an oligoclonal B cell stimulation, and secondary autoimmune diseases, in which the immune system is completely normal but some autoantigens are slightly altered, and are thus considered to be foreign. Sjögren's syndrome probably has characteristics of both types of autoimmune disease. The primary autoimmune diseases can be divided into organ-specific autoimmune diseases like thyroiditis, gastritis and adrenalitis, and generalised autoimmune diseases, such as systemic lupus erythematosus (SLE) and rheumatoid arthritis. Sjögren's syndrome has characteristics of both types of primary autoimmune disease, and therefore occupies a central position among the other autoimmune diseases. The focal position of the disease in the present issue of The Netherlands Journal of Medicine is because of the symposium organized for the occasion of the fifth anniversary of the "Dutch Association of Patients with Sjögren's Syndrome", of which this issue is the report.