CCL21 levels were also higher in SSc-PAH patients (n=41) compared to SSc patients with no PH (n=51) by RHC (0.69 ± 0.30ng/ml vs. 0.44 ± 0.21ng/ml, p<0.001) (Figure 4B, i). This evidence concerns the gene CCL21 and systemic sclerosis.