We have rechecked the exome data of the 3 patients for 17 genes known to be associated with PAH (BMPR2, EIF2AK4, TBX4, ATP13A3, GDF2, SOX17, AQP1, ACVRL1, SMAD9, ENG, KCNK3, CAV1, SMAD4, SMAD1, KLF2, BMPR1B, and KCNA5). The gene discussed is KCNA5; the disease is pulmonary arterial hypertension.