Clinical Features and Risk Factors of Rapidly Progressive Systemic Sclerosis in a Single Center in China: Anti-RNA Polymerase III Antibodies as a Predictor.

Objectives: Systemic sclerosis (SSc) have been classified in two clinical subsets (diffuse and limited) based on the extend of skin thickening. In this study, we classified a novel subset of SSc defined rapidly progressive systemic sclerosis (RPSSc), which based on the rate of skin thickening progression and the progressive of interstitial lung disease (ILD). We aimed to evaluate RPSSc clinical characteristics and predictive factors in a Chinese single center.

Method: Overall, 75 patients diagnosed with SSc, classified into RPSSc (n = 14) and non-rapidly progressive SSc (non-RPSSc, n = 61) were retrospectively included in the study. Clinical characteristics, disease severity and autoantibodies were collected. Logistic regression, least absolute shrinkage, and selection operator (LASSO) regression analysis was used to identify RPSSc predictors. Receiver operating characteristic (ROC) analysis and Delong test was conducted to evaluate and compare different indexes.

Results: RPSSc rate was 18.7%. ILD (64.3%), cardiac involvement (42.9%) were the most common organ system involvement of RPSSc, while Raynaud's phenomenon incidence significantly decreased. Disease duration (12 vs 72, months), sex (42.9% vs 11.5%, male %), SSc subset (85.7% vs 27.9%, diffuse cutaneous SSc (dsSSc) %), modified Rodnan total skin score (mRSS) (20.5 vs 6), Raynaud's phenomenon (64.3% vs 98.4%), cardiac involvement (42.9% vs 18%), higher incidence with malignancy (28.6% vs 1.6%) and positive anti-RNA polymerase III antibodies (ARA) (64.3% vs 1.6%) were statistically significant differences among the RPSSc groups and non-RPSSc groups (p < 0.05). Univariate analysis showed that positive ARA, male, dsSSc and malignancy were RPSSc risk factors, while long-disease duration, Raynaud's phenomenon was RPSSc protective factors. ARA was the strongest factor associated to RPSSc (OR 108, 95% CI 11.287-1033.327, p < 0.001). LASSO logistic regression model identified six factors: Disease duration, dsSSc, malignancy, cardiac involvement, positivity of ARA were RPSSc risk factors, Raynaud's phenomenon was RPSSc protective factors.

Conclusions: RPSSc is an SSc clinical category which should be accounted for early detection of organ involvement and close follow-up of malignancy. ARA might be used as a predictor for RPSSc and organ involvement.