7% of patients with IPAH has a family history [3], and about 70% of these have long been recognized and are usually due to mutations in BMPR2, or much less commonly, 2 other members of the transforming growth factor superfamily, activin-like kinase type 1 (ALK1) and endoglin (ENG) [1]. Here, ACVRL1 is linked to idiopathic pulmonary arterial hypertension.