ACVRL1 and pulmonary arterial hypertension: Previous large survey confirmed that BMPR2 (15.3%), ACVRL1 (activin receptor-like kinase 1 (ALK1)) (0.9%), ENG (endoglin) (0.6%), and KCNK3 (potassium channel subfamily K member 3) (0.4%) are causal mutations of PAH [9].