The FGF23/α-Klotho index was significantly reduced in SSc patients (0.013 (0.0081–0.025) vs. 0.055 (0.038–0.095); p < 0.001), and its log10 correlated (r = 0.35; p < 0.001) with disease activity score (Eular2017). The gene discussed is KL; the disease is systemic sclerosis.