Beyond overlap: a Ro52-driven glandular-pulmonary phenotype at the interface of Sjögren disease and anti-synthetase syndrome in a multicentre cohort

Background While Sjögren disease (SjD) overlap is known to modulate the clinical-serologic manifestations of other connective tissue diseases, the association with anti-synthetase syndrome (ASyS) has been seldom described in Caucasian cohorts. Anti-Ro52 autoantibodies, shared by both conditions, may blur early diagnostic attribution, particularly when glandular symptoms precede myositis-spectrum features. Objectives To characterize the clinical phenotype, serological profile, and disease trajectory of patients fulfilling classification criteria for both SjD and ASyS. Methods We conducted a multicentre retrospective study (2018-2025) across three Italian referral centres, including patients meeting both the 2016 ACR/EULAR SjD criteria and the Connor’s/provisional CLASS classification criteria for ASyS. Clinical features, serology, interstitial lung disease (ILD) characteristics, treatments, and outcomes were systematically collected. SjD activity was assessed using the ESSDAI and an adapted ESSDAI excluding the classic ASyS triad (pulmonary, articular and muscular domains). Results Seventeen female patients of Caucasian ethnicity were identified. At the time of connective tissue disease diagnosis, 7 were classified as SjD and 10 received concomitant diagnoses; all reported early sicca symptoms. Regarding serology, anti-Ro52 antibodies were detected in all patients, most often (88%) in the absence of anti-Ro60 antibodies. Anti-synthetase antibodies were present in all cases, mainly non-Jo-1 specificities (77%), while anti-Jo-1 was observed in a minority of patients (23%). ILD was the leading organ involvement (14/17, 82%), typically with acute/subacute onset and NSIP or NSIP/OP patterns. ILD drove treatment decisions and accounted for four deaths, whereas most survivors showed stabilization or mild improvement under immunosuppressive treatment. Systemic assessment indicated a predominantly ASyS-driven phenotype: although ESSDAI was moderately elevated (median 15, IQR 7.5-21), the adapted ESSDAI markedly decreased (median 5, IQR 0-6.5), reflecting limited SjD-specific systemic activity. Conclusions The SjD-ASyS overlap seem characterized by a coherent clinical-serological phenotype, defined by anti-Ro52-positive sicca presentation, non-Jo1 anti-ARS autoantibodies and early interstitial lung disease. Pulmonary involvement represents the main driver of disease course and outcomes in this subset. Recognition of this pattern may improve early identification of ASyS in Ro52-positive SjD presentations. Further prospective studies are warranted to clarify whether this subset reflects a distinct phenotype within the ASyS spectrum rather than a coincidental overlap of two independent diseases.