PAH can be further categorized into idiopathic PAH (without any identifiable cause, 6th World Symposium class 1.11) and heritable PAH (defined by mutations in specific genes, 6th World Symposium class 1.21), the most common affecting bone morphogenetic protein receptor type II (BMPR2).2 The gene discussed is BMPR2; the disease is pulmonary arterial hypertension.