To assess the clinical, laboratory, and salivary gland ultrasound (SGUS) characteristics of elderly-onset of primary Sjögren's syndrome (EopSS).

We included pSS patient from two referral hospitals over a 4-year period. The SGUS scores (0–48) and SG volumes were assessed. Clinical, laboratory, and SGUS data were compared according to age at onset: EopSS (≥65 years), adult-onset (AopSS) (≥40 and <65 years), and young-onset (YopSS) (<40 years).

This cross-sectional study included a total of 221 patients, 43 (19.5%) of which had EopSS. Subjective sicca symptoms, results of the Schirmer's test, and unstimulated salivary flow rate revealed no significant differences between the groups. EopSS patients presented a significantly higher frequency of interstitial lung disease (ILD) (EopSS: 51.2% vs. AopSS: 13.5% vs. YopSS: 8.7%, P<0.001) and lower frequency of arthritis (7% vs. 22.6% vs. 39.1%, P<0.01). They also had significantly lower positivity of anti-Ro/SSA (51.2%) and anti-La/SSB (7.0%) and lower levels of rheumatoid factor, C4, and IgG. The EopSS group had significantly lower SGUS positivity (defined as total scores ≥14) (44.2% vs. 64.5% vs. 78.3%, P<0.05), lower SGUS scores, and smaller submandibular gland volume.

We report a specific phenotype of EopSS, characterised by high prevalence of ILD, less involvement of the peripheral joint, and low biological activity. SGUS evaluation showed less parenchymal abnormalities but more atrophic changes in major SGs in EopSS patients. Considering the low positivity of anti-Ro/SSA and SGUS in EopSS, SG biopsy remains the only way to confirm the diagnosis of pSS, especially in elderly patients.