RESUMO
OBJECTIVES: To further investigate the clinical characteristics and circulating lymphocyte profiles of patients with early-onset primary Sjögren's syndrome (pSS). METHOD: Data of 333 patients with pSS were analysed retrospectively. Early onset was defined as a pSS diagnosis at an age of 35 years or younger. The clinical, laboratory and immunophenotypic profiles of peripheral blood lymphocyte subsets were compared between early- and later-onset pSS. RESULTS: Thirty-six (10.81%) patients matched the definition of early-onset pSS, with age at disease onset being 28.97 (5.53) years. Elevated serum IgG level (77.14% vs 31.16%, P <0.001), low C3 (41.67% vs 20.20%, P =0.004) and C4 levels (27.78% vs 6.40%, P <0.001), anti-SSA positivity (91.67% vs 51.85%, P <0.001) and anti-SSB positivity (50% vs 20.54%, P <0.001) were more frequent in early-onset patients. The frequencies of hematological (80.56% vs 52.53%, P =0.001), renal (19.44% vs 5.05%, P =0.005) and mucocutaneous involvement (50% vs 22.56%, P <0.001) were significantly higher in the early-onset pSS group, which showed a higher 2010 EULAR SS Disease Activity Index (ESSDAI) [11(6.25-17) vs 7(3-12); P =0.003], compared with the later-onset group. In addition, profound CD4+ T-cell lymphopenia was found in patients with early-onset. CONCLUSIONS: Patients with early-onset pSS have distinctive clinical manifestations and greater activation of the cellular immune system, present with more severe clinical symptoms and immunological features, have increased activation of circulating T cells and have an unfavourable prognosis. Thus, they require more positive treatment with glucocorticoids and/or immunosuppressants and merit closer follow-up and regular monitoring.