Clinical and immunologic predictors of scleroderma renal crisis in Japanese systemic sclerosis patients with anti-RNA polymerase III autoantibodies

Abstract

Objective: To identify predictive factors for scleroderma renal crisis (SRC) in patients with anti-RNA polymerase III (anti-RNAP III) antibodies.

Methods: A total of 583 adult Japanese patients with systemic sclerosis (SSc) were screened for anti-RNAP III using a commercially available enzyme-linked immunosorbent assay (ELISA) kit. RNAP subsets were further identified by immunoprecipitation (IP) assays. The association of clinical and immunologic factors with SRC was examined by logistic analyses.

Results: In this cohort, 37 patients (6%) were positive for anti-RNAP III, as determined by anti-RNAP III-specific ELISA. Further IP assays revealed that 19 patients were positive for anti-RNAP I/III, 17 for anti-RNAP I/II/III, and 1 for anti-RNAP III. SRC occurred in a total of 17 (2.9%) of 583 patients, with a significantly higher frequency in anti-RNAP III-positive SSc patients (9 of 37 [24%]) than those without anti-RNAP III (8 of 546 [1%]) (odds ratio [OR] 21.6 [95% confidence interval (95% CI) 7.8-60.3], P < 0.00001). Our multivariate analyses using the Cox proportional hazards regression model revealed that anti-RNAP I/II/III positivity (OR 11.0 [95% CI 1.6-222.8], P = 0.0118) and an ELISA index for anti-RNAP III of ≥157 (OR 2.4 × 10(9) [95% CI 2.1-uncalculated], P = 0.0093) were independent factors associated with the development of SRC.

Conclusion: Our findings indicate that anti-RNAP III is associated with SRC, as reported previously. In addition, the presence of anti-RNAP II in combination with anti-RNAP I/III (anti-RNAP I/II/III) and a higher ELISA index for anti-RNAP III may be associated with the development of SRC in SSc patients with anti-RNAP III.