Characteristics and Survival of Anti–U1 RNP Antibody–Positive Patients With Connective Tissue Disease–Associated Pulmonary Arterial Hypertension

Objective Pulmonary arterial hypertension (PAH) is a severe complication of connective tissue diseases (CTDs). This study aimed to investigate the clinical and hemodynamic characteristics and survival of anti–U1 RNP–positive patients with CTD-associated PAH, with a focus on systemic sclerosis (SSc)–associated PAH. Methods We implemented a prospective database that included patients with CTD-associated PAH for whom there were clinical, autoantibody, and mortality data. We compared clinical and hemodynamic characteristics to anti–U1 RNP antibody status. We then assessed whether anti–U1 RNP antibodies could be a prognostic factor in CTD-associated PAH with a focus on SSc-associated PAH. Results We studied a total of 342 patients with CTD-associated PAH, of whom 36 (11%) were anti–U1 RNP antibody positive. Anti–U1 RNP–positive patients were younger and less functionally impaired than were anti–U1 RNP–negative patients in CTD- and SSc-associated PAH. Hemodynamic parameters were similar in anti–U1 RNP–positive and anti–U1 RNP–negative patients. In CTD-associated PAH, anti–U1 RNP positivity was associated with decreased mortality in univariable analysis (hazard ratio 0.34 [95% confidence interval 0.18–0.65], P < 0.001). In multivariable analysis, anti–U1 RNP positivity was also associated with decreased mortality (hazard ratio 0.44 [95% confidence interval 0.20–0.97], P = 0.043) independently of age, sex, functional parameters, lung involvement, and hemodynamic parameters. Results were similar in SSc-associated PAH, although the association between anti–U1 RNP positivity and survival did not reach significance in univariable (hazard ratio 0.47 [95% confidence interval 0.22–1.02], P = 0.055) and multivariable (hazard ratio 0.47 [95% confidence interval 0.20–1.11], P = 0.085) analyses. Conclusion Anti–U1 RNP positivity was associated with distinct clinical characteristics and survival in CTD- and SSc-associated PAH. While hemodynamic parameters were similar in anti–U1 RNP–positive and anti–U1 RNP–negative patients, our results suggest that anti–U1 RNP positivity could be a factor protecting against mortality in CTD- and SSc-associated PAH.