Image analysis of fibrosis in labial salivary glands of patients with systemic autoimmune diseases. Close correlation of lobular fibrosis to seropositive rheumatoid arthritis and increased anti-CCP and RF titres in the serum

Lobular fibrosis in labial salivary glands of patients with systemic autoimmune disease is a rarely examined and rather neglected histological change. Its significance and disease association is poorly understood. Our aim was to explore the clinical correlations of fibrosis in labial salivary gland samples using objective methods and laboratory parameters. Labial salivary gland samples from more than 300 patients over a 3-year period were selected from the archives of the pathology department, histologically examined, digitised, image analysed and statistically evaluated to identify the presence and intensity of lobular fibrosis, its relation to age, clinical diagnoses of systemic autoimmune disease and the presence of rheumatoid factor (RF), anti-cyclic citrullinated peptide (CCP), antinuclear antibodies (ANAs), and anti-dsDNA serum markers. Significant correlation was found between lobular fibrosis and the presence of autoimmune disease (p = 0.023), mainly seropositive rheumatoid arthritis (p < 0.001). Also significant association was found between the fibrosis and the presence of serum anti-CCP (p < 0.001) and IgA/IgG/IgM-RF (p < 0.001, p < 0.001 and p = 0.008, respectively). Significant association was explored between the anti-dsDNA positivity and the negative histology groups (p = 0.033) and between the ANA positivity and the inflammation only group (p = 0.021). The results suggest that lobular fibrosis tends to associate to certain systemic autoimmune diseases, mainly seropositive rheumatoid arthritis, and seems to be rare in labial salivary gland biopsies of autoimmune diseases characterised by presence of anti-dsDNA. The close correlation of ANA positivity and the inflammation only histology was not surprising, since the majority of patients (62%) have Sjögren's syndrome, known for its inflammatory infiltrate. These findings emphasise that evaluation of lobular fibrosis and inflammation in histological samples of labial salivary gland biopsies are equally important.