Following the identification of BMPR2 haploinsufficiency as a molecular mechanism of disease, additional causal variants were described in genes encoding the ALK1 (ACVRL1) and Endoglin (ENG) receptors, which have been observed in association with hereditary haemorrhagic telangiectasia (HHT). The gene discussed is ENG; the disease is hereditary hemorrhagic telangiectasia.