We queried gene expression for twelve known PAH risk genes (ACVRL1, BMPR2, CAV1, EIF2AK4, ENG, KCNK3, KDR, NOTCH1, SMAD4, SMAD9, SOX17, TBX4) and the two new candidate risk genes (FBLN2, PDGFD). The gene discussed is TBX4; the disease is pulmonary arterial hypertension.