BMPR2 and pulmonary arterial hypertension: Variants in BMPR2 and other genes in the BMPR2 signaling pathway (ACVRL1, ENG, SMAD9, and GDF2) are causal in ~12–20% of sporadic, idiopathic PAH (IPAH) cases and rarely in PAH associated with other diseases (APAH) or medication/toxins [6].