ACVRL1 and idiopathic pulmonary arterial hypertension: To validate the risk effects of GDF2, they performed WES in an independent replication cohort of 80 IPAH cases and in a second gene-based burden analysis (cases: n = 80; controls: n = 8624), BMPR2, GDF2 and ACVRL1 were again identified as the top three disease-associated genes.