KLK1 and pulmonary arterial hypertension: The associations were stronger for IPAH than all PAH; while KLK1 was the only gene to exceed the Bonferroni-corrected threshold for significance (OR = 13.9, p = 2.00E−07 for all PAH; OR = 26.2, p = 1.00E−07 for IPAH), five additional family members had an enrichment rate of rare deleterious variants greater than 2.0 for IPAH (Additional file 11: Table S6B).