Hereditary Haemorrhagic Telangiectasia

Hereditary haemorrhagic telangiectasia (HHT) is a vascular dysplasia inherited as an autosomal dominant trait and caused by loss-of-function pathogenic variants in genes encoding proteins of the BMP signalling pathway. Up to 90% of disease-causal variants are observed in ENG and ACVRL1, with SMAD4 and GDF2 less frequently responsible for HHT. In adults, the most frequent HHT manifestations relate to iron deficiency and anaemia owing to recurrent epistaxis (nosebleeds) or bleeding from gastrointestinal telangiectases. Arteriovenous malformations (AVMs) in the lungs, liver and the central nervous system cause additional major complications and often complex symptoms, primarily due to vascular shunting, which is right-to-left through pulmonary AVMs (causing ischaemic stroke or cerebral abscess) and left-to-right through systemic AVMs (causing high cardiac output). Children usually experience isolated epistaxis; in rare cases, childhood complications occur from large AVMs in the lungs or central nervous system. Management goals encompass control of epistaxis and intestinal bleeding from telangiectases, screening for and treatment of iron deficiency (with or without anaemia) and AVMs, genetic counselling and evaluation of at-risk family members. Novel therapeutics, such as systemic antiangiogenic therapies, are actively being investigated. Although HHT is associated with increased morbidity, the appropriate screening and treatment of visceral AVMs, and the effective management of bleeding and anaemia, improves quality of life and overall survival.