Thus, in order to verify the expression differences of hub genes IL-7R, LCK, and HDAC1 between SSc and SSc-PAH, we used GSE22356 and GSE33463 as test sets and GSE19617 as the validation sets, which include 21 SSc patients and 15 SSc-PAH patients. This evidence concerns the gene HDAC1 and pulmonary arterial hypertension.