In PAH several common genetic variants were found to contribute to phenotypic heterogeneity among patients with rare causal mutations in BMPR2. Polymorphisms at BMPR2125 , TGF-β1126 and sex hormones loci104 were shown to contribute to variable gene expression and at least partially explain phenotypic variation between BMPR2 mutation carriers. The gene discussed is BMPR2; the disease is pulmonary arterial hypertension.