The 6th WSPH listed BMPR2, EIF2AK4, TBX4, ATP13A3, GDF2, SOX17, AQP1, ACVRL1, SMAD9, ENG, KCNK3 and CAV1 mutations as higher level of evidence and SMAD4, SMAD1, KLF2, BMPR1B and KCNA5 with lower level of evidence of association with primary PAH (2). This evidence concerns the gene KLF2 and pulmonary arterial hypertension.