Heterozygous germ-line mutations in the BMPR2 gene, encoding the bone morphogenetic protein type II receptor (BMPR-II), underlie ∼70% of heritable (HPAH) and 20% of idiopathic (IPAH) cases2, 3, 4. The gene discussed is BMPR2; the disease is idiopathic pulmonary arterial hypertension.