In this study, we have identified and characterized 15 out of 57 PAH patients carrying more than one pathogenic mutation in several genes related to PAH, such as BMPR2, ENG, ACVRL1 and KCNA5. Twelve of these patients harboured at least one mutation in BMPR2, reinforcing the role of this gene in the development of PAH. This evidence concerns the gene KCNA5 and pulmonary arterial hypertension.