KL and systemic sclerosis: At t0, SSc patients have significant higher serum levels of FGF-23 [18.7 ± 6.4 pg/ml versus 3.6 ± 2.2 pg/ml, p < 0.001, d = 3.1], Klotho [5.1 ± 0.8 pg/ml versus 2.3 ± 0.6 pg/ml, p < 0.001, d = 3.9] and NGAL [20.9 ± 2.6 pg/ml versus 14.5 ± 1.7 pg/ml, p < 0.001, d = 2.9] compared to HC (Fig. 1A-C).