There are a number of clinical subtypes of PAH, including: idiopathic PAH; PAH associated with another disease, typically connective tissue diseases and congenital heart diseases (CHD) with large systemic to pulmonary arterial shunts; and heritable (H) PAH, which is most commonly caused by mutations in the bone morphogenetic protein receptor type II (Bmpr2) gene. This evidence concerns the gene BMPR2 and pulmonary arterial hypertension.