TGFB1 and pulmonary arterial hypertension: The bone morphogenetic protein type 2 receptor gene (BMPR2; MIM #600799), a member of the transforming growth factor (TGF-β) superfamily, was the first causal gene identified in PAH and is mutated in approximately 10 to 40% of IPAH patients and 80% of patients with HPAH.