In a small proportion of PAH patients, mutations have been identified in ACVRL1, ENG, SMAD9 [OMIM 603295] and the genes encoding BMP9 (GDF2 [OMIM 605120]) and BMP10 (BMP10 [OMIM 608748]; Drake et al., 2011; Eyries et al., 2019; Gräf et al., 2018; Machado et al., 2015; Shintani et al., 2009; Wang et al., 2019). Here, ACVRL1 is linked to pulmonary arterial hypertension.