Objective: To determine the prevalence of keratoconjunctivitis sicca and xerostomia related to Sjögren's syndrome (SS) in asymptomatic patients with diagnosed autoimmune thyroid diseases (AITD); and to investigate whether the immunopathologies of sialadenitis observed in AITD associated SS and primary SS are similar.
Methods: One hundred seventy-six patients diagnosed with AITD (88 with Graves' disease, 40 Hashimoto's thyroiditis, 48 primary myxedema) were tested for keratoconjunctivitis sicca (Schirmer's test and rose bengal staining) and for xerostomia (salivary scintigraphy and labial salivary gland biopsy). Immunohistopathological studies were performed on cryostat sections of bucal mucosa biopsies using antibodies to CD3, CD4, CD8, CD20, CD14, CD25, LFA-1, ICAM-3 HLA class II, tumor necrosis factor-alpha, interleukin 1, and interferon-gamma.
Results: Nineteen of 52 (37%) patients with AITD fulfilled the criteria for xerostomia and 39/170 (23%) for keratoconjunctivitis sicca. Features of SS were diagnosed in 43 of 176 (24%) patients with AITD, with similar prevalence in Graves' (20%). Hashimoto's thyroiditis (27%), and primary myxedema (29%). In AITD associated SS, infiltrating lymphocytes were mainly CD3+ T lymphocytes, with a CD4/CD8 ratio of 2:1. In most patients infiltrating lymphocytes expressed activation markers, HLA class II molecules, and interleukin 2 receptor (CD25). In some patients HLA class II was inappropriately expressed in the epithelial gland cells.
Conclusion: The finding that a third of patients with AITD have SS features confirms that AITD and SS are mutually associated. Together with the similarity of immunopathology of sialadenitis in AITD associated SS in primary SS, this supports the theory that SS and AITD are 2 autoimmune diseases closely related pathogenetically.