ACVRL1 and pulmonary arterial hypertension: Genetic studies have identified the presence of causal mutations of genes related to PAH development such as bone morphogenetic protein receptor (BMPR2), T-box 4 (TBX4), activin A receptor-like type 1 (ACVRL1), endoglin (ENG), small mothers against decapentaplegic homolog 9 (SMAD9), caveolin-1 (CAV1), potassium channel subfamily K member 3 (KCNK3), ATPase 13A3 (ATP13A3), SRY-box 17 (SOX17), aquaporin 1 (AQP1), growth differentiation factor 2/BMP9 (GDF2), and eukaryotic translation initiation factor 2 alpha kinase 4 (EIF2AK4) [91].