SMAD9 and pulmonary arterial hypertension: In this study, 8 patients (8/45 = 17.8%) had WSPH-listed PAH-related gene (other than BMPR2) variants (1 with ACVRL1, 1 with ENG, 1 with SMAD9, 1 with SMAD1, 1 with ATP13A3 and 3 with AQP1) (Table 1 and Figure 1).