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. The gene discussed is ACVRL1; the disease is hereditary hemorrhagic telangiectasia.