Hereditary haemorrhagic telangiectasia (HHT) is diagnosed clinically by the Curaçao Criteria of spontaneous recurrent nosebleeds, mucocutaneous telangiectasia at characteristic sites, visceral involvement (arteriovenous malformations (AVMs); gastrointestinal telangiectasia) and family history.1 Early diagnosis is important to enable AVM screening and preventative treatments.2–5 HHT is caused by loss-of-function DNA variants in ENG, ACVRL1, SMAD4 or GDF2,6–9 though older manuscripts describing linkage to additional loci10 11 continue to be referenced heavily. Here, SMAD4 is linked to hereditary hemorrhagic telangiectasia.