The link between deregulated BMP signaling, pericyte-endothelial cell communication and HHT disease progression remains to be determined but an important clue may come from the fact that HHT individuals who have ACVRL1 mutations are predisposed to the development of PAH (Girerd et al., 2010; Gore et al., 2014). Here, ACVRL1 is linked to hereditary hemorrhagic telangiectasia.