TGFB1 and hereditary hemorrhagic telangiectasia: AVMs are hallmarks of HHT, a human disease caused by autosomal dominant mutations in genes of the TGF-β signaling pathway, in particular endoglin or ACVRL1 (activin receptor-like kinase 1).37 In HHT, AVMs commonly form in the nose, lungs, brain, or the liver and affected individuals often suffer from nasal and gastrointestinal bleedings.