Anti-RNPC-3 antibody predicts poor prognosis in patients with interstitial lung disease associated to systemic sclerosis

Objective: To analyse the prevalence, the clinical characteristics, the overall survival and the event-free survival (EFS) of SSc patients who express anti-U11/U12 RNP (RNPC-3) antibodies. Methods: A total of 447 SSc patients from Barcelona (n = 286) and Milan (n = 161) were selected. All samples were tested using a particle-based multi-analyte technology. We compared anti-RNPC-3 positive and negative patients. Epidemiological, clinical features and survival were analysed. End-stage lung disease (ESLD) was defined if the patient developed forced vital capacity <50% of predicted, needed oxygen therapy or lung transplantation. EFS was defined as the period of time free of either ESLD or death. Results: Nineteen of 447 (4.3%) patients had anti-RNPC-3 antibodies and interstitial lung disease (ILD) was more frequent (11, 57.9% vs 144, 33.6%, P =0.030) in individuals with anti-RNPC-3 antibodies. More patients reached ESLD in the positive group (7, 36.8% vs 74, 17.3%, P = 0.006), and a higher use of non-glucocorticoid immunosuppressive drugs was observed (11, 57.9% vs 130, 30.4%, P = 0.012). Anti-RNPC-3 positive patients had lower EFS, both in the total cohort (log-rank P =0.001), as well as in patients with ILD (log-rank P = 0.002). In multivariate Cox regression analysis, diffuse cutaneous subtype, age at onset, the presence of ILD or pulmonary arterial hypertension and the expression of anti-RNPC-3 positivity or anti-topo I were independently associated with worse EFS. Conclusion: The presence of anti-RNPC-3 was associated with higher frequency of ILD and either ESLD or death. These data suggest anti-RNPC-3 is an independent poor prognosis antibody in SSc, especially if ILD is also present.