With the development of genetic technology such as whole-genome and whole-exome sequencing, several key genes were identified in patients with familial PAH and IPAH, especially BMPR2. Further analysis from cohorts of patients with CTD-PAH, mainly with SSc-PAH, has identified additional susceptibility genes including TBX4, ABCC8, KCNA5, and GDF2/BMP9 [9, 29]. Here, TBX4 is linked to pulmonary arterial hypertension.