Within the PAH category, several subgroups of disease are recognized, including idiopathic PAH, heritable PAH (links to genetic mutations in BMPR2 [5] and ALK-1 [6] have been found), connective tissue disease-associated PAH (e.g., PAH associated with systemic sclerosis or systemic lupus erythematous), PAH associated with congenital heart disease, and portopulmonary hypertension [7]. Here, BMPR2 is linked to pulmonary arterial hypertension.