There is growing data to support this conclusion, as recent studies comparing HPAH patients with a BMPR2 mutation to IPAH patients showed that: (a) HPAH patients were less likely to respond to acute vasodilator testing [10,11]; (b) HPAH patients presented at a younger age and with more severe hemodynamic compromise at diagnosis [11,12]; (c) HPAH patients had a shorter time to death or lung transplantation. This evidence concerns the gene BMPR2 and heritable pulmonary arterial hypertension.