SMAD9 and pulmonary arterial hypertension: After the revision, from the 15 genes that were found in 10 or more abstracts, five of these genes (BMPR2, ACVRL1, ENG, EDN1, and SMAD9) were found to have some evidence of mutations in PAH, one gene (NOS3) was found to be mutated in a related disease, and one gene, serotonin transporter (SLC6A4), was classified as negative evidence.