STAT4 and systemic sclerosis: IRF5 rs2004640 T allele (OR 1.30 (95% CI 1.10–1.54), pcorr = 0.015), IRF5 rs10488631 C allele (OR 1.48 (95% CI 1.14–1.92), pcorr = 0.022) and STAT4 rs7574865 T allele (OR 1.43 (95% CI 1.18–1.73), pcorr = 0.0015) were risk factors for SSc.