Meanwhile, Takeda et al. [11] and colleagues conducted the research regarding bilirubin and mortality in 18 patients with idiopathic PAH (IPAH) and 19 with connective tissue disease-associated PAH (CTD-PAH) and found hyperbilirubinemia and total bilirubin concentration to be risk predictors of death independently of WHO functional classification and brain natriuretic peptide (BNP), respectively. This evidence concerns the gene NPPB and idiopathic pulmonary arterial hypertension.