Hamit Küçük, İbrahim Vasi, İbrahim Karaduman, Abdulsamet Erden
Anatolian Current Medical Journal - 2025;7(6):913-918
Aims: Systemic sclerosis-overlap syndrome (SSc-OS) constitutes a distinct clinical phenotype within the spectrum of systemic sclerosis, marked by unique immunological and clinical characteristics that differentiate it from the classical subsets. The present study aimed to characterise the demographic, serological, and organ involvement patterns of patients with SSc-OS, and to assess their disease manifestations and prognostic trajectories in comparison with diffuse cutaneous and limited cutaneous SSc. Methods: This study included patients followed at the Gazi University Hospital Rheumatology Department between January 2010 and July 2025. SSc-OS was defined as patients fulfilling classification criteria for systemic sclerosis together with other autoimmune diseases as rheumatoid arthritis, polymyositis, and or Sjögren's syndrome. Baseline and 1-year characteristics were compared between SSc and SSc-OS. Results: A total of 160 patients were included: 68 diffuse cutaneous (dcSSc), 67 limited cutaneous (lcSSc), and 25 SSc-OS. Age at disease onset was lower in dcSSc (42.5+/-13.7 years) compared with lcSSc (50.6+/-13.7) and SSc-OS (47.2+/-13.9; p=0.003). Anti-topoisomerase I positivity was highest in dcSSc (83.8%) versus lcSSc (43.3%) and SSc-OS (16%; p=0.001), whereas anti-centromere was most frequent in lcSSc (41.8%; p=0.001) and anti-SSa in SSc-OS (44%; p=0.002). Interstitial lung disease (ILD) occurred in 89.7% of dcSSc, 76% of SSc-OS, and 56.7% of lcSSc (p=0.001), with extensive disease more common in dcSSc (61.7%; p=0.001). Myopathy was higher in SSc-OS (44%) and dcSSc (35.3%) than lcSSc (12.1%; p=0.001). Immunosuppressive therapy was most frequent in dcSSc (88.2% vs. 35.8% lcSSc and 60% SSc-OS; p=0.001). At one year, SSc-OS patients showed greater improvements in force vital capacity (FVC) and diffusing capacity for carbon monoxide (DLco), though not statistically significant. Mortality occurred in 25% of dcSSc, 14.9% of lcSSc, and 8% of SSc-OS (p=0.113); Kaplan-Meier analysis demonstrated numerically better survival in SSc-OS (mean 25.3 years) compared with lcSSc (19.8) and dcSSc (19.5; log-rank p=0.249). Conclusion: This study identified SSc-OS in 15.6% of patients, most commonly SSc-Sjögren's. Distinct autoantibody profiles and prominent musculoskeletal involvement differentiated SSc-OS from classical subsets. While dcSSc showed the highest ILD burden and lcSSc was linked to pulmonary arterial hypertension, SSc-OS demonstrated intermediate pulmonary disease and numerically better survival, supporting its recognition as a clinically distinct phenotype within the SSc spectrum.
