Whilst Zhu et al. [25] identified KLK1 and GGCX as new candidate risk genes for IPAH, suggesting new pathogenic mechanisms outside of the TGF-β/BMP signalling pathway, further research needs to be conducted to better understand these findings, especially in larger cohorts of similar phenotypic characteristics. Here, KLK1 is linked to idiopathic pulmonary arterial hypertension.