Age and onset timing of Raynaud's phenomenon and first non-Raynaud symptom as prognostic factors in systemic sclerosis: a retrospective analysis from the Italian national multicenter Systemic Sclerosis Progression INvestiGation registry of the Italian Society for Rheumatology (SPRING-SIR)

Background: The sequence and temporal relationship between Raynaud's phenomenon (RP) and the first non-Raynaud's sign/symptom (NRP) in systemic sclerosis (SSc) have been partially investigated. Objectives: To evaluate whether the mode and ages of clinical onset are associated with disease endotype and survival in SSc. Design: We included SSc patients from the Systemic sclerosis Progression INvestiGation registry of the Italian Society of Rheumatology (SPRING-SIR) registry in a cohort study, with post hoc cross-sectional and longitudinal analysis. Methods: Patients were grouped based on age-RP and age-NRP quartiles. Additionally, categories were defined based on mode of onset: RP group-RP onset at least 1 year before NRP; Simultaneous group-RP onset within the same year of NRP; NRP group-RP onset after at least 1 year after NRP. Comparisons were made using Chi-square and ANOVA tests. Logistic, linear, and multinomial regression models were applied to assess associations, while Kaplan-Meier curves and Cox regression were used to assess mortality. Results: A total of 1748 patients were eligible: 682 (39.0%) in the RP group, 1026 (58.8%) in the simultaneous group, and 39 (2.2%) in the NRP group. A higher prevalence of anti-centromere antibodies was found In the RP group, while the simultaneous group had more diffuse cutaneous SSc (dcSSc), anti-topoisomerase-I antibodies, and higher Rodnan's skin score (mRSS). The NRP group presented higher prevalence of pulmonary arterial hypertension. On logistic regression, the simultaneous group was associated with a higher prevalence of dcSSc compared to the RP group (odds ratio, 1.491, 95% confidence interval (CI): 1.032-2.154). Younger age at RP onset was associated with lower systolic pulmonary artery pressure and mRSS. In 943 patients with available follow-up (median 24 months), the simultaneous group had higher mortality compared to the RP group (hazard ratio, 1.975, 95% CI: 1.002-3.893). Conclusion: The timing of RP and NRP onset may help define SSc endotype and survival. Patients with simultaneous RP-NRP onset have more severe disease features and higher mortality risk, emphasizing the relevance of onset timing in disease stratification.