Differences in clinical phenotypes of primary Sjögren's syndrome depending on early or late onset.

BACKGROUND: Previous research suggests that systemic involvement in primary Sjögren's syndrome (pSS) is a marker of disease prognosis. OBJECTIVES: To evaluate pSS disease activity and the clinical phenotype of pSS patients depending on the age at diagnosis with long-term follow-up. MATERIAL AND METHODS: The study group consisted of patients diagnosed with pSS based on the 2016 pSS classification criteria. RESULTS: The study group consisted of 46 patients with early-onset pSS (≤35 years of age) and 32 patients with late-onset pSS (≥65 years of age). The study group was identified from a total of 228 patients diagnosed with pSS. There were no differences regarding the frequency of eye and mouth dryness, focus score (FS) ≥1 or anti-SSA/SSB antibodies depending on age. Rheumatoid factor (RF) was more common among older patients (p > 0.05). In the overall assessment of disease activity using European League Against Rheumatism (EULAR) Sjögren Syndrome Disease Activity Index (ESSDAI), no differences related to age were observed on the first and last visit (after 36 months on average). Lymphadenopathy and changes in the hematology domain (p < 0.05) were more common in patients with the early-onset phenotype. Changes in the lungs and musculoskeletal system occurred regardless of age. CONCLUSIONS: Patients with early-onset pSS differ from those with late-onset pSS in terms of higher incidence of peripheral lymphadenopathy and cytopenia. The involvement of lung tissue and joints as well as dryness symptoms are common in pSS regardless of age. The RF plays a role in the pathomechanism of pSS development.