Monoallelic mutations of the ACVRL1 gene encoding a cell-surface receptor for the TGF-β superfamily of ligands and expressed on endothelial cells are known to be responsible for HHT (Vivanti et al., 2018; Duran et al., 2018); they are also reported to be associated with isolated VGAM. The gene discussed is ACVRL1; the disease is hereditary hemorrhagic telangiectasia.