Of note, beyond heterozygous BMPR2 germ line mutations in familial PAH, both idiopathic PAH and associated PAH (APAH) due to interstitial lung disease, connective tissue disease, or congenital heart disease are associated with lower levels of BMPR2 expression and signaling [20,21]. The gene discussed is BMPR2; the disease is pulmonary arterial hypertension.