Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant vascular disorder characterized by alterations to key proteins within the transforming growth factor beta (TGF-β) signaling pathway, including endoglin, activin receptor-like kinase 1 (ALK1), SMAD4, and bone morphogenetic protein 9 (BMP9), which are encoded by the ENG, ACVRL1, SMAD4, and GDF2 genes, respectively (Cerdà et al., 2024; Faughnan et al., 2020). The gene discussed is SMAD4; the disease is hereditary hemorrhagic telangiectasia.