GDF2 and idiopathic pulmonary arterial hypertension: Variants in growth differentiation factor 2 (GDF2), encoding the ligand of BMPR2/ACVRL1 (BMP9), contribute to ~ 1% of PAH (mostly IPAH) cases in European-enriched cohorts [7, 8] and more frequently in Chinese patients (~ 6.7%) [15].