ACVRL1 and pulmonary arterial hypertension: Similarly, LKB1 may have an impact on vascular diseases where defects in BMP signaling have been known to play an important role, such as pulmonary arterial hypertension caused by defects in the BMP type II receptor and hereditary hemorrhagic telangiectasia caused by defects in the type I receptor ACVRL1/ALK1 and the co-receptor endoglin [54].