Based on the small relative risks and associated confidence intervals from the UK cohort (RR = 0.37, CI 0.06–1.47 for ATP13A3; RR = 0.19, CI 0.004–1.53 for AQP1), it was not unexpected that that by chance we would observe no association with these genes and PAH. This evidence concerns the gene AQP1 and pulmonary arterial hypertension.