Laboratory evaluation of patients with Sjögren's syndrome.
Sjögren's syndrome (SS) is a chronic autoimmune disorder characterized by lymphocytic infiltration of the lacrymal and salivary glands, leading to severe dryness of eyes (keratoconjunctivitis sicca) and mouth (xerostomia). SS may exist as a primary disorder (1 degree-SS) or in association with other autoimmune diseases including rheumatoid arthritis (RA), systemic lupus erythematosus or progressive systemic sclerosis (scleroderma). Diagnosis of 1 degree-SS is confirmed by minor salivary gland biopsy and the presence of circulating autoantibodies. Minor salivary gland biopsies exhibit focal lymphocytic infiltrates that are present in the majority of lobules. Incorrect methods of biopsy and failure to determine the average focus score are common causes for false-positive and false-negative biopsies. SS patients frequently have a positive antinuclear antibody test due to presence of SS-A (Ro) and SS-B (La) autoantibodies. Molecular analysis has revealed multiple "SS-A" proteins (60 kd, 54 kd, 52 kd) that react with sera from SS patients, as well as a 48 kd SS-B protein. Rheumatoid factor (anti-IgG Fc antibody) in 1 degree-SS patients exhibits restriction in its light chain-associated idiotype, in contrast to RA patients where no restriction of idiotype was detected. Other autoantibodies found in a subpopulation of SS patients include anti-ADP ribose polymerase, anti-cardiolipin, anti-mitochondrial, anti-mitotic spindle apparatus, anti-parietal cell, and anti-thyroid associated antibodies. Due to the high frequency of dryness syndromes in patients due to other causes (ranging from drug side effects to normal aging processes), the use of strict criteria for diagnosis of SS will lead to improved cost-efficient medical care avoiding needless anxiety in the patient.